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A metal complex (R-TAP-Pd(II)) constructed by chiral molecule R-TAP coordinated Pd(II) was used to modify g-C 3 N 4 to promote the separation efficiency of photogenerated carriers. Meanwhile, the R-TAP-Pd(II) acts as an activation site for proton reduction reaction, which enhances the photocatalytic H 2 evolution. [Display omitted] The photocatalytic H 2 production activity of polymer carbon nitride (g-C 3 N 4) is limited by the rapid recombination of photoelectron-hole pairs and slow surface reduction dynamic process. Here, a supramolecular complex (named R-TAP-Pd(II)) was fabricated via self-assembly of (R)-N-(1-phenylethyl)-4-(4-(pyridin-2-yl)-1H-1,2,3-triazol-1-yl)benzamide (R-TAP) with Pd(II) and used to modify g-C 3 N 4. In the R-TAP-Pd(II)@g-C 3 N 4 composite photocatalyst, the spin polarization of R-TAP-Pd(II) can promote charge transfer and inhibit photogenerated carrier recombination, as confirmed by spectral tests and photoelectrochemical performance tests. Electrochemical tests and in situ X-ray photoelectron spectroscopy (XPS) tests proved that the Pd(II) ion in the R-TAP-Pd(II) molecule can serve as active sites to accelerate H 2 production. The R-TAP-Pd(II)@g-C 3 N 4 presented a photocatalytic H 2 generation rate of 1085 μmol g−1 h−1 when exposed to visible light, which was a about 278-fold increase compared with g-C 3 N 4. This work finds a new approach to boost the photocatalytic efficiency of g-C 3 N 4 via supramolecular self-assembly. [ABSTRACT FROM AUTHOR]

[Display omitted] The efficiency of CO 2 photocatalytic reduction is severely limited by inefficient separation and sluggish transfer. In this study, spin polarization was induced and built-in electric field was strengthened via Co doping in the BiVO 4 cell to boost photocatalytic CO 2 reduction. Results showed that owing to the generation of spin-polarized electrons upon Co doping, carrier separation and photocurrent production of the Co-doped BiVO 4 were enhanced. CO production during CO 2 photocatalytic reduction from the Co-BiVO 4 was 61.6 times of the BiVO 4. Notably, application of an external magnetic field (100 mT) further boosted photocatalytic CO 2 reduction from the Co-BiVO 4 , with 68.25 folds improvement of CO production compared to pristine BiVO 4. The existence of a built-in electric field (IEF) was demonstrated through density functional theory (DFT) simulations and kelvin probe force microscopy (KPFM). Mechanism insights could be elucidated as follows: doping of magnetic Co into the BiVO 4 resulted in increased the number of spin-polarized photo-excited carriers, and application of a magnetic field led to an augmentation of intrinsic electric field due to a dipole shift, thereby extending carrier lifetime and suppressing charges recombination. Additionally, HCOO− was a crucial intermediate in the process of CO 2 RR, and possible pathways for CO 2 reduction were proposed. This study highlights the significance of built-in electric fields and the important role of spin polarization for promotion of photocatalytic CO 2 reduction. [ABSTRACT FROM AUTHOR]

[Display omitted] Magnetic semiconductors with both electron charge and spin features exhibit tremendous potential in spintronics. Although defective transition-metal dichalcogenides are promising with induced room temperature (RT) magnetic moments, impacts of the defect type and underlying mechanisms remain unclear. Herein, two strategies involving elemental substitution and epitaxial growth have been explored to synthesize alloyed and hybrid MoSe 2-x S x with lattice distortion and artificial interfaces respectively. Both experimental measurements and first-principle calculations demonstrate induced magnetism in the resultant MoSe 2-x S x with the magnetization intensity closely associated to the atomic structure. The alloyed MoSe 2-x S x exhibits satisfactory structural stability and atomic magnetic moments due to the Mo 4d orbital splitting induced by lattice distortion. Nevertheless, both enhanced RT ferromagnetism and thermomagnetic stability can be achieved for the hybrid MoSe 2-x S x resulted from stronger localized spin polarization at the MoSe 2 /MoS 2 interfaces. As such the work not only sheds light on the mechanisms underlying defect-induced ferromagnetism in transition-metal dichalcogenides, but also proposes an interface engineering strategy to induce significant ferromagnetism for multi-fields including spintronics, multiferroics and valleytronics. [ABSTRACT FROM AUTHOR]

[Display omitted] • The nitrogen vacancies-zinc porphyrin (NVs-ZnTCPP) ultrathin nanosheets was fabricated through a simple surface N 2 plasma treatment. • The optimized NVs-ZnTCPP exhibits superior photocatalytic carbon dioxide (CO 2) reduction activity and selectivity to carbon monoxide (CO). • The promoted photocatalytic performance of NVs-ZnTCPP could be mainly attributed to nitrogen vacancy-induced spin polarization. Metalloporphyrin compounds have excellent electron transfer and visible light absorption ability, demonstrating broad application prospects in the field of photocatalysis. In this work, the nitrogen vacancies (NVs) were successfully introduced into zinc porphyrin (ZnTCPP) ultrathin nanosheets through surface N 2 plasma treatment, which is environmentally friendly and can react in low temperatures. Furthermore, the prepared nitrogen vacancies-zinc porphyrin (NVs-ZnTCPP) materials exhibited excellent photocatalytic CO 2 reduction activity and selectivity, specifically, the CO production rate of ZnTCPP-1 (N 2 plasma treatment, 1 min) achieved as high as 12.5 µmol g–1h−1, which is about 2.7 times greater than that of untreated ZnTCPP. Based on the experimental and density functional theory calculation (DFT) results, it is found that the promoted photocatalytic performance of NVs-ZnTCPP could be mainly attributed to nitrogen vacancy-induced spin polarization by reducing the reaction barriers and inhibiting the recombination of photoexcited carriers. This work provides a new perspective for the construction of vacancy-based metalloporphyrin, and further explores the intrinsic mechanism between the electron spin property and the performance of the photocatalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • Improving CoPc catalyst performance by identifying potential atomic-style linkers. • Calculations suggest improved CO 2 ERR performance for the NH, PH and S linkers. • Unoccupied spin-down d z 2 orbital components facilitate initial CO 2 adsorption. • Contrary to previous experiments, the NH 2 linker shows weak bonding to CoPc. We investigate the CO 2 electroreduction reaction (CO 2 ERR) using first principles calculations, for the active site tuning of cobalt phthalocyanine (CoPc) via distinct atomic linker species which immobilize CoPc on a carbon nanotube (CNT) substrate. Eight different linker species are studied, along with the effect of linker hydrogenation. Superior reaction performance is predicted for the NH, S and PH linkers, which show activated CO 2 adsorption. This results from spin polarization causing unoccupied d z 2 spin-down states of the cobalt active site at, or above, the Fermi level. Using an 'on-catalyst' reaction scheme, calculated activation barriers for COOH formation and CO desorption are lower for the CoPc-PH-CNT system compared to the CoPc-NH-CNT system and CoPc remains attached to PH-CNT throughout the reaction. We thus expect the PH linker system to have similar or better CO 2 ERR performance compared to the NH and S linker systems but at a slightly higher electrode potential. [ABSTRACT FROM AUTHOR]

The excellent photocatalytic performance was attributed to upshift of d-band center, and highly energetic electrons induced by the CB flexibility alleviated the photoinduced electron recombination in defective MIL-125. [Display omitted] Solar energy is becoming the most promising option to mitigate the energy crisis in the future and can be applied in renewable and economical technologies such as water splitting and pollutants degradation. The promotion of the electronic energetic level is considered an efficient method to enhance the photocatalytic performance of semiconductor materials for solar energy conversion. The highly energetic electrons exhibit a remarkable reduction ability by virtue of the electronic spin polarization, which is associated with the conduction band (CB) position. Thus, the regulation of the CB position due to the redistribution of electrons by means of defect engineering presents potential. Here, a series of titanium-based metal–organic frameworks (Ti-based MOFs) named MIL-125-m% containing different extents of defects are reported to enable photocatalytic activity under simulated sunlight and visible light illumination for remarkably enhanced photocatalytic hydrogen evolution and pollutant degradation. The experimental results illustrated that MIL-125–5 % exhibited a superior photocatalytic hydrogen evolution rate (16507.27 μmol·g−1·h−1), much higher than that of MIL-125-0 % (1.444 μmol·g−1·h−1). The excellent photocatalytic performance was attributed to upshift of d-band center, which strengthened the adsorption of H*, facilitating the H 2 evolution reaction. In addition, the degradation rate of MIL-125-5 % was up to twice the original rate, for the highly energetic electrons induced by the CB flexibility alleviated the photoinduced electron recombination in defective MIL-125. The strategy of defect engineering provides a new path to control the flexibility of the CB position by electronic spin polarization on adjustable metal–organic frameworks (MOFs), and the photocatalytic effect is changed accordingly. [ABSTRACT FROM AUTHOR]

The excellent photocatalytic performance was attributed to upshift of d-band center, and highly energetic electrons induced by the CB flexibility alleviated the photoinduced electron recombination in defective MIL-125. [Display omitted] Solar energy is becoming the most promising option to mitigate the energy crisis in the future and can be applied in renewable and economical technologies such as water splitting and pollutants degradation. The promotion of the electronic energetic level is considered an efficient method to enhance the photocatalytic performance of semiconductor materials for solar energy conversion. The highly energetic electrons exhibit a remarkable reduction ability by virtue of the electronic spin polarization, which is associated with the conduction band (CB) position. Thus, the regulation of the CB position due to the redistribution of electrons by means of defect engineering presents potential. Here, a series of titanium-based metal–organic frameworks (Ti-based MOFs) named MIL-125-m% containing different extents of defects are reported to enable photocatalytic activity under simulated sunlight and visible light illumination for remarkably enhanced photocatalytic hydrogen evolution and pollutant degradation. The experimental results illustrated that MIL-125–5 % exhibited a superior photocatalytic hydrogen evolution rate (16507.27 μmol·g−1·h−1), much higher than that of MIL-125-0 % (1.444 μmol·g−1·h−1). The excellent photocatalytic performance was attributed to upshift of d-band center, which strengthened the adsorption of H*, facilitating the H 2 evolution reaction. In addition, the degradation rate of MIL-125-5 % was up to twice the original rate, for the highly energetic electrons induced by the CB flexibility alleviated the photoinduced electron recombination in defective MIL-125. The strategy of defect engineering provides a new path to control the flexibility of the CB position by electronic spin polarization on adjustable metal–organic frameworks (MOFs), and the photocatalytic effect is changed accordingly. [ABSTRACT FROM AUTHOR]

[Display omitted] • Oxygen activation and •O 2 – oxidation sites are constructed in g-C 3 N 4 , which promote the 100 % conversion of •O 2 – to 1O 2. • The water bridge indirectly enhanced the oxidation effect of 1O 2 on isopropanol in H 2 O 2 generation. • Spin polarization and water bridge jointly modify the electronic structures of 1O 2 and isopropanol and thus significantly enhancing the interaction between them. • The 1O 2 can react with isopropanol to produce H 2 O 2 in the most favourable way under the coordinated regulation of spin polarization and water bridge. The indirect attack mechanism of 1O 2 on electron donors (ED) provides a new idea for improving photoproduction of H 2 O 2 (PHO). Inspired by this, we constructed oxygen activation and •O 2 – oxidation sites in g-C 3 N 4 to promote the 100% conversion of •O 2 – to 1O 2 for PHO. Based on experimental data, we unexpectedly discovered the coordinated regulation of spin polarization and water bridge (CRSPWB) in H 2 O 2 generation reaction by theoretical calculation. The 1O 2 can react with ED to produce H 2 O 2 in the most favourable way under the CRSPWB, which modifies the electronic structures of 1O 2 and ED to maximize the interaction between them. Besides, water bridge indirectly enhances the oxidation effect of 1O 2 on ED. Thus, corresponding reaction barrier for H 2 O 2 generation is reduced to as low as −0.07 eV. This work provides in-depth insights into the attack behavior of 1O 2 in H 2 O 2 generation and brand-new guidance for improving PHO. [ABSTRACT FROM AUTHOR]

Spectral diffusion of electron spin polarization plays a key part in dynamic nuclear polarization (DNP). It determines the distribution of polarization across the electron spin resonance (ESR) line and consequently the polarization that is available for transfer to the nuclear spins. Various authors have studied it experimentally by means of electron–electron double resonance (ELDOR) and proposed and used macroscopic models to interpret these experiments. However, microscopic models predicting the rate of spectral diffusion are scarce. The present article is an attempt to fill this gap. It derives a spectral diffusion equation from first principles and uses Monte Carlo simulations to determine the parameters in this equation. The derivation given here builds on an observation made in a previous article on nuclear dipolar relaxation: spectral diffusion is also spatial diffusion and the random distribution of spins in space limits the former. This can be modelled assuming that rapid flip-flop transitions between a spin and its nearest neighbour do not contribute to diffusion of polarization across the ESR spectrum. The present article presents predictions of the spectral diffusion constant and shows that this limitation may lower the spectral diffusion constant by several orders of magnitude. As a check the constant is determined from first principles for a sample containing 40 mM TEMPOL. Including the limitation then results in a value that is close to that obtained from an analysis of previously reported ELDOR experiments. [Display omitted] • Electron spectral diffusion in spin system is also spatial diffusion. • Random spatial distribution of spins decreases spectral diffusion rate. • Decrease modelled by excluding flip-flop transitions with nearest neighbours. • Spins not on speaking terms treated introducing low effective concentration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Constructing sulfur vacancies on SnS 2 to induce spin polarization that avoids electron-hole recombination. • Superoxide radicals destroy bacterial cell membranes. • Sv-SnS 2 has broad-spectrum bactericidal properties under visible light. • Sv-SnS 2 has good biocompatibility. With the emergence and massive spread of antibiotic-resistant bacteria, it is urgent to develop new bactericidal technologies. Photocatalytic sterilization is a technique that uses solar energy to produce reactive oxygen species to kill pathogenic bacteria, and ROS effects depends on the charge separation characteristics of photocatalysts, so the development of strategies to promote charge separation is crucial. Here, we use the strategy of introducing sulfur vacancy on SnS 2 , effectively improving the separation of photogenerated charge. The femtosecond transient absorption results confirm that the charge lifetime of SnS 2 (Sv-SnS 2) after the introduction of the sulfur vacancy is 13.33 times that of pristine SnS 2. The DFT theoretical results confirm that sulfur vacancy causes spin polarization. It is easier to separate when the spin direction of the electrons and holes changes. In addition, the sulfur vacancy also expands the light absorption range and exposes the surface catalytic site. These phenomena lead to a higher ROS yield of Sv-SnS 2 (confirmed by electron paramagnetic resonance results). Thus, Sv-SnS 2 killed 99.99 % of E. coli and MRSA within 40 min under visible-light illumination. This efficient bactericidal performance can be attributed to improved photogenerated charge separation. This study confirms the effectiveness of sulfur vacancy strategy to improve charge separation and extend charge life, and applies it to the killing of antibiotic resistant bacteria, providing a new idea for the killing of resistant bacteria. [ABSTRACT FROM AUTHOR]

Pulse electron double resonance (PELDOR), also called double electron–electron resonance (DEER), is a technique capable of measuring the strength of electron spin dipolar interactions, revealing spin–spin distance distributions in ordered and disordered solid materials. Previous work has shown that PELDOR signals acquire an out-of-phase component under conditions of high electron spin polarization, such as at low temperatures and high fields. In this paper, we show theoretically and experimentally that the size and sign of this effect depends on the macroscopic shape of the sample and its orientation in the external magnetic field. This effect is caused by dipolar interactions between distant spins and provides new insights into the fundamental physics of PELDOR. [Display omitted] • PELDOR signals of highly polarized samples are predicted to depend on sample shape. • Experiments at 70% electron spin polarization (5 K, 6.4 T) confirm this prediction. • The effect is due to very long-range electron spin dipole–dipole interactions. [ABSTRACT FROM AUTHOR]

Herein, structural, optical, magnetic, electronic, and thermoelectric (TE) characteristics of cubic spinels Ln 2 MnSe 4 (Ln = Yb, Lu) are examined by DFT + U. Enthalpy of formation (ΔH f) for both spinels are negative (−3.189 and −2.251 eV for Yb 2 MnSe 4 and Lu 2 MnSe 4 , correspondingly), which supports thermodynamical stability for both spinels. Spin dependent band structures and density of state (DOS) disclose the half metallic and magnetic semiconducting nature for both Ln 2 MnSe 4 (Ln = Yb, Lu) spinels, respectively, with direct bandgaps of 1.44 eV in spin up and metallic in spin down for Yb 2 MnSe 4 whereas Lu 2 MnSe 4 has 0.5/1.5 eV in spin up/down channel. Optical response of Ln 2 MnSe 4 (Ln = Yb, Lu) spinels is also determined. At 0 eV, the computed results of refractive index n (ω) for Yb 2 MnSe 4 /Lu 2 MnSe 4 are 12.0/2.89, respectively. For Yb 2 MnSe 4 and Lu 2 MnSe 4 peak value of σ(ω) are calculated as 7813.08 at 7.03 eV and 7532.71 (1/Ωcm) at 6.47 eV, respectively. To assess the temperature dependent transport behavior of both compounds, thermoelectric (TE) characteristics including power factor (PF), Seebeck coefficient (S), thermal conductivity (k/τ), electrical conductivity (σ/τ) and figure of merit (ZT) are determined. Maximum ZT values for Yb 2 MnSe 4 and Lu 2 MnSe 4 are 0.18 and 0.79 at 800 K, correspondingly. Results show that Yb 2 MnSe 4 is suitable contender spintronics due to 100% spin polarization at Fermi level whereas Lu 2 MnSe 4 is useful addition to magnetic semiconductor family having potential applications in opto-electronic and TE devices. Spin dependent band structures and density of state (DOS) disclose the half metallic and magnetic semiconducting nature for both Ln 2 MnSe 4 (Ln = Yb, Lu) spinels, respectively, with direct bandgaps of 1.44 eV in spin up and metallic in spin down for Yb 2 MnSe 4 whereas Lu 2 MnSe 4 has 0.5/1.5 eV in spin up/down channel. Optical response of Ln 2 MnSe 4 (Ln = Yb, Lu) spinels is also determined. At 0 eV, the computed results of refractive index n (ω) for Yb 2 MnSe 4 /Lu 2 MnSe 4 are 12.0/2.89, respectively. For Yb 2 MnSe 4 and Lu 2 MnSe 4 peak value of σ(ω) are calculated as 7813.08 at 7.03 eV and 7532.71 (1/Ωcm) at 6.47 eV, respectively. Maximum ZT values for Yb 2 MnSe 4 and Lu 2 MnSe 4 are 0.18 and 0.79 at 800 K, correspondingly. Results show that Yb 2 MnSe 4 is suitable contender spintronics due to 100% spin polarization at Fermi level whereas Lu 2 MnSe 4 is useful addition to magnetic semiconductor family having potential applications in opto-electronic and TE devices. [Display omitted] • ΔH f confirm the thermal stability for both compounds. • Yb 2 MnSe 4 /Lu 2 MnSe 4 are half metallic and magnetic semiconducting nature, respectively. • Maximum ZT values for Yb 2 MnSe 4 /Lu 2 MnSe 4 are 0.18/0.79, correspondingly. • Both spinels are applicants for opto-electronic and TE applications. [ABSTRACT FROM AUTHOR]

First principles calculations were carried out to examine the spin-polarized electronic and optical characteristics of novel Ba 2 TaXO 6 (X = Co, Fe, In) double perovskites in the monoclinic phase, employing the full-potential linearized augmented plane wave technique (FP-LAPW) based on the density functional theory (DFT). To calculate the total energy, the Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA) were used. The electronic study with the TB-mBJ approach shows a metallic nature for Ba 2 TaCoO 6 and a half-metallic nature for Ba 2 TaFeO 6 and Ba 2 TaInO 6 materials. The calculated density of states, nearly show similar features for all the materials. The PDOS were calculated, which displays the contribution of several electronic states for these compounds in the distribution. Additionally, in the optical spectra, the dielectric functions, absorption coefficients, refractive indexes, extinction coefficients, energy loss function, and reflectivity parameters were calculated in the energy range 0–14 eV. The optical parameters demonstrate that the materials are the potential candidates for opto-electronics devices. Figure: Spin-Polarized optical parameters for Ba 2 TaFeO 6 double perovskite. [Display omitted] • A metallic nature for Ba 2 TaCoO 6 and a half-metallic nature for Ba 2 TaFeO 6 and Ba 2 TaInO 6 is observed. • The calculated density of states, nearly display a similarity trend. • The energy loss was maximum in energy region 0.6–6.0 eV range. • The peaks in ε 2 (ω) are linked to various inter-band transitions. • These double perovskites show substantial absorption in UV region. [ABSTRACT FROM AUTHOR]

• A (S + 1/2) loss in many correlation and polarization-transfer experiments of quadrupole nuclei S. • Level-crossings of satellite transition and rf frequency under MAS complicate the spin dynamics of quadrupole nuclei. • NMR method development, high magnetic fields, efficient and high-power probes are important to quadrupole nuclei. High magnetic field can dramatically increase the spectral resolution and sensitivity of quadrupole nuclei S > 1/2 by the reduction of the second-order quadrupole broadening. A brief overview and outlook on spectral acquisition, the importance of high magnetic field, inter-nuclei distance measurement, various 2D separation and correlation methods of quadrupole nuclei are presented. The complications and consequences of spin dynamics under rf irradiation for the (2S + 1) level system and level-crossing with the satellite transition frequencies under magic-angle spinning are discussed. There is a scaling down of (S + 1/2) to the efficiency of many experiments in comparison with a spin-1/2 due to the fact that only two central transition spin states out of the (2S + 1) levels contribute to polarization transfer and spin correlation. [ABSTRACT FROM AUTHOR]

We describe a useful method for measuring the internuclear distances within arbitrarily selected pairs of like nuclei in dipolar-coupled multi-spin systems. The method uses a combination of the zero-quantum shift-evolution-assisted selective homonuclear recoupling (ZQ-SEASHORE) technique developed by Hu and Tycko [ J. Chem. Phys. 2009, 131, 045101] and double-frequency-selective radio-frequency pulse. The double-frequency-selective pulse inverts polarizations of two spins simultaneously, and thus applications of the method presented here are only limited by the spectral resolution, and not by the number of interacting spins. Our experiments demonstrate the validity of the method and present analytical expressions for the dephasing curve. Image 1 • Internuclear distances are measured between arbitrarily chosen like nuclei in dipolar-coupled multi-spin systems. • The double-frequency-selective pulses are used to select the spins; the ill effects of dipolar truncation are avoided. • An analytical treatment is developed for fitting the experimentally obtained dipolar dephasing curves. [ABSTRACT FROM AUTHOR]

Solid-state NMR spectroscopy is a powerful technique for the characterization of the atomic-level structure and dynamics of materials. Nevertheless, the use of this technique is often limited by its lack of sensitivity, which can prevent the observation of surfaces, defects or insensitive isotopes. Dynamic Nuclear Polarization (DNP) has been shown to improve by one to three orders of magnitude the sensitivity of NMR experiments on materials under Magic-Angle Spinning (MAS), at static magnetic field B 0 ≥ 5 T, conditions allowing for the acquisition of high-resolution spectra. The field of DNP-NMR spectroscopy of materials has undergone a rapid development in the last ten years, spurred notably by the availability of commercial DNP-NMR systems. We provide here an in-depth overview of MAS DNP-NMR studies of materials at high B 0 field. After a historical perspective of DNP of materials, we describe the DNP transfers under MAS, the transport of polarization by spin diffusion and the various contributions to the overall sensitivity of DNP-NMR experiments. We discuss the design of tailored polarizing agents and the sample preparation in the case of materials. We present the DNP-NMR hardware and the influence of key experimental parameters, such as microwave power, magnetic field, temperature and MAS frequency. We give an overview of the isotopes that have been detected by this technique, and the NMR methods that have been combined with DNP. Finally, we show how MAS DNP-NMR has been applied to gain new insights into the structure of organic, hybrid and inorganic materials with applications in fields, such as health, energy, catalysis, optoelectronics etc. Image 1 • An overview of MAS DNP-NMR in material research is presented. • MAS DNP enhances the sensitivity of solid-state NMR by several orders of magnitude. • This sensitivity gain facilitates the observation of surfaces, insensitive isotopes and diluted species. • This technique has notably been applied for pharmaceuticals, polymers, porous materials and nanoparticles. [ABSTRACT FROM AUTHOR]

• Magnetic-field dependent photoluminescence of NV− centers in diamonds is modelled. • A calculation method is proposed to account for coherent polarization transfer. • The method reproduces sharp dips from avoided crossings in the field dependence. • Groups of such dips, LAC lines, can be modelled theoretically. We propose an efficient method for calculating level anti-crossing spectra (LAC spectra) of interacting paramagnetic defect centers in crystals. By LAC spectra we mean the magnetic field dependence of the photoluminescence intensity of paramagnetic color centers: such field dependences often exhibit sharp features, such as peaks or dips, originating from LACs in the spin system. Our approach takes into account the electronic Zeeman interaction with the external magnetic field, dipole-dipole interaction of paramagnetic centers, hyperfine coupling of paramagnetic defects to magnetic nuclei and zero-field splitting. By using this method, not only can we obtain the positions of lines in LAC spectra, but also reproduce their shapes as well as the relative amplitudes of different lines. As a striking example, we present a calculation of LAC spectra in diamond crystals containing negatively charged NV centers. [ABSTRACT FROM AUTHOR]

In recent years, the search for new Dirac half-metallic materials has been one of the hotspots in the field of spintronics because they have very good physical properties, such as massless Dirac fermions and full spin polarization. In this study, using density function theory combined with the quasi-harmonic Debye model, we show that perovskite-type dysprosium manganite is a novel half metal with multiple Dirac cones. A detailed study of the electronic, magnetic, and thermodynamic properties of DyMnO 3 was carried out. Furthermore, the effects of uniform strain, the on-site Coulomb interaction U , spin-orbit coupling, and hole and electron doping on the multiple Dirac cones and full spin polarization were investigated. We should point out that such a spin-polarized Dirac material is rare among perovskite-type compounds. Hence, we hope that, through this work, this kind of material will receive more extensive attention in future studies. In this study, using density function theory combined with the quasi-harmonic Debye model, we show that perovskite-type dysprosium manganite is a novel half metal with multiple Dirac cones. Moreover, in order to test whether the material has a long spin coherence length, we studied the effect of SOC on the band structure. Image 1 [ABSTRACT FROM AUTHOR]

We investigate solid-state dynamic nuclear polarization of 13C and 15N nuclei using monoradical trityl OX063 as a polarizing agent in a magnetic field of 14.1 T with magic angle spinning at ∼100 K. We monitored the field dependence of direct 13C and 15N polarization for frozen [13C, 15N] urea and achieved maximum absolute enhancement factors of 240 and 470, respectively. The field profiles are consistent with polarization of 15N spins via either the solid effect or the cross effect, and polarization of 13C spins via a combination of cross effect and solid effect. For microcrystalline, 15N-enriched tryptophan synthase sample containing trityl radical, a 1500-fold increase in 15N signal was observed under microwave irradiation. These results show the promise of trityl radicals and their derivatives for direct polarization of low gamma, spin-½ nuclei at high magnetic fields and suggest a novel approach for selectively polarizing specific moieties or for polarizing systems which have low levels of protonation. Image 1 • Dynamic nuclear polarization (DNP) of 13C and 15N nuclei by trityl OX063 is demonstrated at 14.1 T and ∼100 K under magic angle spinning. • DNP agree with 15N polarization via either the solid effect or the cross effect, and 13C polarization via a combination of cross effect and solid effect. • Trityl radicals and their derivatives can directly polarize low gamma, spin-½ nuclei at high magnetic fields. • Direct polarization enables selectively polarizing specific moieties or polarizing systems which have low levels of protonation. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Overhauser-enhanced Magnetic Resonance Imaging is used for oxygen imaging in vivo. • Overhauser signal enhancement depends on contrast agent and oxygen concentrations. • Overhauser signal enhancement increased with a higher contrast agent concentration. • The presence of a paramagnetic compounds decreases an Overhauser signal enhancement. • Polarization leakage factor is important for correct oxygen values assessment. Abstract Overhauser-enhanced Magnetic Resonance Imaging (OMRI) is a double resonance technique applied for oxygen imaging in aqueous samples and biological tissues. In this report, we present an improved OMRI approach of oxygen measurement using the single line "Finland" trityl spin probe. Compared to a traditional approach, we introduced an additional mechanism of leakage of spin polarization due to an interaction of a spin system with oxygen. The experimental comparison of the new approach with an oxygen-dependent leakage factor to a traditional approach performed in phantom samples in vitro, and mouse tumor model in vivo, shows improved accuracy of determination of oxygen and contrast agent concentrations. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • First rapid-scan EPR in 200 GHz frequency range. • Extremely fast (3 × 105 THz/s) and broad (20 GHz) frequency sweeps. • Access to very short relaxation times ≈ 1 ns. • Easy to expand the frequency range up to 1 THz. Abstract Gaining access to electron spin dynamics at (sub-)THz frequencies is highly challenging. However, this information is highly relevant for the understanding and development of spin polarization agents in dynamic nuclear polarization methods and single-molecule magnets for quantum computation. Here we demonstrate the first rapid-scan EPR experiment in 200 GHz frequency region. A voltage controlled oscillator (VCO) generated fast sinusoidal frequency sweeps with scan rates up to 3 × 10 5 THz/s after the frequency multiplication, which is equal to 10 7 T/s in field representation. Such high scan rates provide access to extremely short relaxation times T 2 = 2 π × sweep rate - 0.5 ≈ 1 ns. The absence of a microwave cavity allowed us to perform multi-frequency experiments in the 170–250 GHz range. A further advantage of a cavity-less approach is the possibility to use vast sweeps, which in turn, allows the deconvolution using a linear sweep function. The deconvoluted spectra obtained with this method are identical to the slow-rate spectrum. We find spin-spin relaxation times of several nanoseconds for pure LiPc samples in this frequency range. These values cannot be obtained by means of conventional pulsed EPR methods. [ABSTRACT FROM AUTHOR]

We present a theoretical study of quantum phases and quantum phase transitions occurring in non-Hermitian P T -symmetric superconducting qubits chains described by a transverse-field Ising spin model. A non-Hermitian part of the Hamiltonian is implemented via imaginary staggered longitudinal magnetic field, which corresponds to a local staggered gain and loss terms. By making use of a direct numerical diagonalization of the Hamiltonian for spin chains of a finite size N , we explore the dependencies of the energy spectrum, including the energy difference between the first excited and the ground states, the spatial correlation function of local polarization (z -component of local magnetization) on the adjacent spins interaction strength J and the local gain (loss) parameter γ. A scaling procedure for the correlation length ξ allows us to establish a complete quantum phase diagram of the system. We obtain two quantum phases for J < 0 , namely, P T -symmetry broken antiferromagnetic state and P T -symmetry preserved paramagnetic state, and the quantum phase transition line between them is the line of exception points. For J > 0 the P T -symmetry of the ground state is retained in a whole region of parameter space of J and γ , and a system shows two intriguing quantum phase transitions between ferromagnetic and paramagnetic states for a fixed parameter γ > 1. We also provide the qualitative quantum phase diagram γ − J derived in the framework of the Bethe–Peierls approximation that is in a good accord with numerically obtained results. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ramsey apparatus using protons spins in flowing water as probe particles. • Sensitive to magnetic field effects below 100 pT. • Suitable for testing radio-frequency effects like the dressed spin states. • Potential co-magnetometer in other experiments. • Intended for use in searches for new long-range interactions. We present an apparatus that applies Ramsey's method of separated oscillatory fields to proton spins in water molecules. The setup consists of a water circuit, a spin polarizer, a magnetically shielded interaction region with various radio frequency elements, and a nuclear magnetic resonance system to measure the spin polarization. We show that this apparatus can be used for Rabi resonance measurements and to investigate magnetic and pseudomagnetic field effects in Ramsey-type precision measurements with a sensitivity below 100 pT. [ABSTRACT FROM AUTHOR]

In this work, we have theoretically investigated the influence of velocity barrier on the spin-valley polarized transport in monolayer (ML) WSe 2 junction with a large spin-orbit coupling (SOC). Both the spin-valley resolved transmission probabilities and conductance are strong dependent on the velocity barrier, as the velocity barrier decreases to 0.06, a spin-valley polarization of exceeding 90% is observed, which is distinct from the ML MoS 2 owing to incommensurable SOC. In addition, the spin-valley polarization is further increased above 95% in a ML WSe 2 superlattice, in particular, it's found many extraordinary velocity barrier-dependent transport gaps for multiple barrier due to evanescent tunneling. Our results may open an avenue for the velocity barrier-controlled high-efficiency spin and valley polarizations in ML WSe 2 -based electronic devices. [ABSTRACT FROM AUTHOR]

We report the structural, magnetic and electronic properties of the pristine and single TM atoms X (X = Fe, Ru or Os) doped monolayer WS 2 systems based on first-principle calculations. The results show that the W-S bond shows a stronger covalent bond, but the covalency is obviously weakened after the substitution of W atom with single X atoms, especially for Ru (4d 7 5s 1 ) with the easily lost electronic configuration. The smaller total energies of the doped systems reveal that the spin-polarized states are energetically favorable than the non-spin-polarized states, and the smallest total energy of −373.918 eV shows the spin-polarized state of the Os doped monolayer WS 2 system is most stable among three doped systems. In addition, although the pristine monolayer WS 2 system is a nonmagnetic-semiconductor with a direct band gap of 1.813 eV, single TM atoms Fe and Ru doped monolayer WS 2 systems transfer to magnetic-HM with the total moments M tot of 1.993 and 1.962 μ B , while single TM atom Os doped monolayer WS 2 systems changes to magnetic-metal with the total moments M tot of 1.569 μ B . Moreover, the impurity states with a positive spin splitting energies of 0.543, 0.276 and 0.1999 eV near the Fermi level E F are mainly contributed by X - d xy and X - d x 2 - y 2 states hybridized with its nearest-neighbor atom W - d z 2 states for Fe, Ru and Os doped monolayer WS 2 system, respectively. Finally, we hope that the present study on monolayer WS 2 will provide a useful theoretical guideline for exploring low-dimensional spintronic materials in future experiments. [ABSTRACT FROM AUTHOR]

The spin-polarized first-principles are used to study the surface thermodynamic stability, electronic and magnetic properties in various (001) surfaces of Zr 2 CoSn Heusler alloy, and the bulk Zr 2 CoSn Heusler alloy are also discussed to make comparison. The conduction band minimum (CBM) of half-metallic (HM) bulk Zr 2 CoSn alloy is contributed by Zr A , Zr B and Co atoms, while the valence band maximum (VBM) is contributed by Zr B and Co atoms. The SnSn termination is the most stable surface with the highest spin polarizations P = 77.1% among the CoCo, ZrCo, ZrZr, ZrSn and SnSn terminations of the Zr 2 CoSn (001) surface. In the SnSn termination of the Zr 2 CoSn (001) surface, the atomic partial density of states (APDOS) of atoms in the surface, subsurface and third layers are much influenced by the surface effect and the total magnetic moment (TMM) is mainly contributed by the atomic magnetic moments of atoms in fourth to ninth layers. [ABSTRACT FROM AUTHOR]

A method is proposed for significant improvement of NMR pulse sequences used in high-field SABRE (Signal Amplification By Reversible Exchange) experiments. SABRE makes use of spin order transfer from parahydrogen ( p H 2 , the H 2 molecule in its singlet spin state) to a substrate in a transient organometallic Ir-based complex. The technique proposed here utilizes “re-polarization”, i.e., multiple application of an NMR pulse sequence used for spin order transfer. During re-polarization only the form of the substrate, which is bound to the complex, is excited by selective NMR pulses and the resulting polarization is transferred to the free substrate via chemical exchange. Owing to the fact that (i) only a small fraction of the substrate molecules is in the bound form and (ii) spin relaxation of the free substrate is slow, the re-polarization scheme provides greatly improved NMR signal enhancement, ε . For instance, when pyridine is used as a substrate, single use of the SABRE-INEPT sequence provides ε ≈ 260 for 15 N nuclei, whereas SABRE-INEPT with re-polarization yields ε > 2000 . We anticipate that the proposed method is useful for achieving maximal NMR enhancement with spin hyperpolarization techniques. [ABSTRACT FROM AUTHOR]

We report magic angle spinning (MAS) up to 8.5 kHz with a sample temperature below 6 K using liquid helium as a variable temperature fluid. Cross polarization 13 C NMR spectra exhibit exquisite sensitivity with a single transient. Remarkably, 1 H saturation recovery experiments show a 1 H T 1 of 21 s with MAS below 6 K in the presence of trityl radicals in a glassy matrix. Leveraging the thermal spin polarization available at 4.2 K versus 298 K should result in 71 times higher signal intensity. Taking the 1 H longitudinal relaxation into account, signal averaging times are therefore predicted to be expedited by a factor of >500. Computer assisted design (CAD) and finite element analysis were employed in both the design and diagnostic stages of this cryogenic MAS technology development. Computational fluid dynamics (CFD) models describing temperature gradients and fluid flow are presented. The CFD models bearing and drive gas maintained at 100 K, while a colder helium variable temperature fluid stream cools the center of a zirconia rotor. Results from the CFD were used to optimize the helium exhaust path and determine the sample temperature. This novel cryogenic experimental platform will be integrated with pulsed dynamic nuclear polarization and electron decoupling to interrogate biomolecular structure within intact human cells. [ABSTRACT FROM AUTHOR]

The structural, magnetic and electronic properties of the p-type (group VA elements N, P, As or Sb) and n-type (group VIIA elements Cl, Br, I or At) doped monolayer WS 2 systems have been systematically investigated using the spin-polarized first-principle calculations. The results show that whether p-type or n-type doped monolayer WS 2 systems, the greater the atomic radius of the dopant X, the greater the bond length d X − W and height difference h S , but the smaller the bond angle θ W - X - W . All doped systems are easier to form and more stable under W-rich condition than S-rich condition. Specially, the N- and Cl-doped cases are the most stable in p-type and n-type doped monolayer WS 2 systems, respectively. The total magnetic moment M tot of the N-doped system is 0.773 μ B contributed mainly by N-p orbitals, the total magnetic moments M tot of the P-, As- and Sb-doped systems are all approximately zero, and the total magnetic moments M tot of the Cl-, Br-, I- and At-doped systems are 0.543, 0.810, 0.989 and 0.999 μ B , respectively, contributed mainly by the first nearest-neighbor atom W-d orbitals. Although the pristine monolayer WS 2 system is a nonmagnetic semiconductor, the doped system changes to magnetic semiconductor for N-doped system, nonmagnetic metal for P-, As- and Sb-doped systems, magnetic metal for Cl- and Br-doped systems and magnetic half-metal for I- and At-doped systems. [ABSTRACT FROM AUTHOR]

The heavy metal atoms X (X = Au, Hg, Tl or Pb) doped monolayer WS 2 systems have been studied by using the spin-polarized first-principles calculations. Although pure monolayer WS 2 system is a nonmagnetic semiconductor with a direct band gap of 1.820 eV, the Au and Hg atoms doped monolayer WS 2 systems change to half-metal (HM) ferromagnets with the total magnetic moments 0.697 and 1.776 μ B as well as the smaller spin-down gaps 0.605 and 0.527 eV, respectively, while the Tl and Pb atoms doped monolayer WS 2 systems change to magnetic metal with the total magnetic moment 0.584 μ B and a nonmagnetic metal. From the minimization of the formation energy, we find that it is easy to incorporate these heavy metal atoms into monolayer WS 2 system under S-rich condition, especially for the Au doped monolayer WS 2 system not only easily to be formed but also a HM ferromagnet, and thus the best candidate used in the spintronic devices. [ABSTRACT FROM AUTHOR]

We theoretically investigate the spin-dependent conductance and shot noise properties in graphene based periodic velocity barrier structure under Rashba spin–orbit interaction (RSOI). The system consists of graphene sheet in which the Fermi velocity and the electrostatic potential vary in space. We find that the spin-dependent conductance and shot noise in graphene can be efficiently controlled by tuning the Fermi velocity. Moreover, changing the Fermi velocity allows us to change the positions of the Dirac points. The spin-dependent Fano factor without and with spin flip increases and decreases, respectively with increasing the RSOI strength. When Fermi velocity in the barriers is smaller than the velocity outside the barriers, we find that the Fano factor for outgoing electrons with opposite spins has an oscillatory behavior with respect to the RSOI strength. Specifically, as the number of velocity barriers increases or Fermi velocity decreases the spin polarization increases. [ABSTRACT FROM AUTHOR]

In this paper a five layer organic electronic device with alternately placed ferromagnetic metals and organic polymers: ferromagnetic metal/organic layer/ferromagnetic metal/organic layer/ferromagnetic metal, which is injected a spin-polarized electron from outsides, is studied theoretically using one-dimensional tight binding model Hamiltonian. We calculated equilibrium state behavior after an electron with spin is injected into the organic layer of this structure, charge density distribution and spin polarization density distribution of this injected spin-polarized electron, and mainly studied possible transport behavior of the injected spin polarized electron in this multilayer structure under different external electric fields. We analyze the physical process of the injected electron in this multilayer system. It is found by our calculation that the injected spin polarized electron exists as an electron-polaron state with spin polarization in the organic layer and it can pass through the middle ferromagnetic layer from the right-hand organic layer to the left-hand organic layer by the action of increasing external electric fields, which indicates that this structure may be used as a possible spin-polarized charge electronic device and also may provide a theoretical base for the organic electronic devices and it is also found that in the boundaries between the ferromagnetic layer and the organic layer there exist induced interface local dipoles due to the external electric fields. [ABSTRACT FROM AUTHOR]

[Display omitted] • EasySpin now includes extended simulation capabilities for spin-polarized states. • A flexible and general interface covers states of arbitrary spin multiplicity. • Spin-polarized EPR spectra provide information on photophysical processes. • Simulation allows extraction of information on mechanism and dynamics of formation. • Photoselection effects for excitation with linearly polarized light are included. The EPR spectra of paramagnetic species induced by photoexcitation typically exhibit enhanced absorptive and emissive features resulting from sublevel populations that differ from thermal equilibrium. The populations and the resulting spin polarization of the spectra are dictated by the selectivity of the photophysical process generating the observed state. Simulation of the spin-polarized EPR spectra is crucial in the characterization of both the dynamics of formation of the photoexcited state as well as its electronic and structural properties. EasySpin, the simulation toolbox for EPR spectroscopy, now includes extended support for the simulation of the EPR spectra of spin-polarized states of arbitrary spin multiplicity and formed by a variety of different mechanisms, including photoexcited triplet states populated by intersystem crossing, charge recombination or spin polarization transfer, spin - correlated radical pairs created by photoinduced electron transfer, triplet pairs formed by singlet fission and multiplet states arising from photoexcitation in systems containing chromophores and stable radicals. In this paper, we highlight EasySpin's capabilities for the simulation of spin-polarized EPR spectra on the basis of illustrative examples from the literature in a variety of fields ranging across chemistry, biology, material science and quantum information science. [ABSTRACT FROM AUTHOR]

There have been suggestions that the Pauli exclusion principle alone can lead a non-interacting (free) system of identical fermions to form crystalline structures dubbed Pauli crystals. Single-shot imaging experiments for the case of ultra-cold systems of free spin-polarized fermionic atoms in a two-dimensional harmonic trap appear to show geometric arrangements that cannot be characterized as Wigner crystals. This work explores this idea and considers a well-known approach that enables one to treat a quantum system of free fermions as a system of classical particles interacting with a statistical interaction potential. The model under consideration, though classical in nature, incorporates the quantum statistics by endowing the classical particles with an effective interaction potential. The reasonable expectation is that possible Pauli crystal features seen in experiments may manifest in this model that captures the correct quantum statistics as a first order correction. We use the Monte Carlo simulated annealing method to obtain the most stable configurations of finite two-dimensional systems of confined particles that interact with an appropriate statistical repulsion potential. We consider both an isotropic harmonic and a hard-wall confinement potential. Despite minor differences, the most stable configurations observed in our model correspond to the reported Pauli crystals in single-shot imaging experiments of free spin-polarized fermions in a harmonic trap. The crystalline configurations observed appear to be different from the expected classical Wigner crystal structures that would emerge should the confined classical particles had interacted with a pair-wise Coulomb repulsion. [ABSTRACT FROM AUTHOR]

In this work, we present a detailed investigation of the influences of intrinsic spin-orbit coupling (ISOC) as well as Rashba spin-orbit coupling (RSOC) on the spin-resolved transport properties and net spin polarization of molybdenum disulfide (MoS 2 ) nanoribbons including different configurations. For this reason, we generalize the tight-binding model by including the effects of the ISOC on all the atoms and a RSOC induced by a vertical electric field. The results predict a noticeable spin polarization in along to the field for the armchair MoS 2 nanoribbon close to the Fermi level, which is originated mostly from edge states. Where as, the induced spin polarization in the zigzag MoS 2 ribbons is much smaller than that of the considered armchair ones. Contrary to the RSOC, which it can not introduce significant spin polarization in the ZMoS 2 the ribbon with width about 1–2 nm, the combination effect of an exchange field and Rashba spin-orbit interaction induces a spin-selective current especially close to the Fermi level. The numerical results may be useful to engineer and design magnetic-field-free spintronic devices based on the MoS 2 nanoribbons. [ABSTRACT FROM AUTHOR]

We study the behaviors of both Hartree and correlation energies of undoped gapped armchair graphene nanoribbon using random phase approximation in the context of Hubbard model Hamiltonian. Specially, the effects of spin polarization and gap parameter on electron density dependence of Hartree and correlation energies of armchair graphene nanoribbon has been addressed. Our results show the variation of gap parameter leads to considerable effect on correlation and Hartree energy behavior of spin unpolarized gapped graphene in the middle electron density region. However local Hubbard interaction parameter affects the behaviors of Hartree and correlation energy on the whole range of electron density in zero magnetization case. We also show that a considerable reduction has been observed for density dependence of Hartree and correlation energies of spin polarized gapped graphene nanoribbon. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hyperpolarized 129Xe MRI permits high-sensitivity in-vivo imaging of human lungs. • Improved SNR and longer T 2 * at low field suggests optimum field strength below 0.5 T. • Advances in manufacturing & computing resulted in improved low field MRI hardware. • Theory, applications & challenges of low field hyperpolarized 129Xe MRI are reported. • Informed predictions are made on the future directions and growth of this field. Magnetic Resonance Imaging (MRI) is dictated by the magnetization of the sample, and is thus a low-sensitivity imaging method. Inhalation of hyperpolarized (HP) noble gases, such as helium–3 and xenon-129, is a non-invasive, radiation-risk free imaging technique permitting high resolution imaging of the lungs and pulmonary functions, such as the lung microstructure, diffusion, perfusion, gas exchange, and dynamic ventilation. Instead of increasing the magnetic field strength, the higher spin polarization achievable from this method results in significantly higher net MR signal independent of tissue/water concentration. Moreover, the significantly longer apparent transverse relaxation time T 2 * of these HP gases at low magnetic field strengths results in fewer necessary radiofrequency (RF) pulses, permitting larger flip angles; this allows for high-sensitivity imaging of in vivo animal and human lungs at conventionally low (<0.5 T) field strengths and suggests that the low field regime is optimal for pulmonary MRI using hyperpolarized gases. In this review, theory on the common spin-exchange optical-pumping method of hyperpolarization and the field dependence of the MR signal of HP gases are presented, in the context of human lung imaging. The current state-of-the-art is explored, with emphasis on both MRI hardware (low field scanners, RF coils, and polarizers) and image acquisition techniques (pulse sequences) advancements. Common challenges surrounding imaging of HP gases and possible solutions are discussed, and the future of low field hyperpolarized gas MRI is posed as being a clinically-accessible and versatile imaging method, circumventing the siting restrictions of conventional high field scanners and bringing point-of-care pulmonary imaging to global facilities. [ABSTRACT FROM AUTHOR]

Present review focuses the investigation carried out in order to understand the interface structure of magnetic tunnel junction (MTJ) by considering Fe/MgO/Fe as prototype structure. Tunneling magnetoresistence (TMR) of MTJ is affected by the spin polarization of ferromagnetic layers. This phenomena is governed by spin dependent tunneling in perfect MTJ. In MTJ with disordered interface, resonance states through interface play an important role. Some important phenomena like perpendicular magnetic anisotropy, spin transfer torques, and electrical switching are also affected by the interface structure. Apart from disorder and lattice mismatch, interface structure is governed by several factors like oxidation, defects, vacancies as well as hybridization among Fe(3 d )-O(2 p ) states. These effects are categorized as ‘chemical effects’. Due to these factors, contribution from interface resonance states dominates which reduces TMR and related properties. A discussion for determination of these effects are highlighted using several techniques like X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. Simulation results reveal modification of TMR via chemical effects occuring at interface in these MTJ. Thus tailoring of chemical effects in controlled manner is discussed to understand the interface assisted phenomena in these structures. Modification of the chemical effects is induced by irradiation of swift heavy ions, thereby, providing an opportunity to correlate chemical effects and TMR of MTJ. [ABSTRACT FROM AUTHOR]

We investigate spin-dependent tunneling time, dwell and group delay time, through monolayer graphene barrier with Rashba spin–orbit interaction in the presence of zigzag and armchair direction strain. It is found that the oscillation amplitude of the dwell time increases by increasing the strain strength. In addition, for the zigzag direction strain the Hartman effect can be observed for the both spin-up and spin-down electrons. When the armchair direction strain is applied to a monolayer graphene the spin polarization increases with increasing the strain strength, whereas for the zigzag direction strain it is zero. In this case, unlike the zigzag direction strain dwell time for the normal incident angle depends on the spin state of electron. [ABSTRACT FROM AUTHOR]

Using spin-polarized density functional theory calculations, we demonstrated that carbon doped boron nitride nanowire (C-doped BNNW) has diverse electronic and magnetic properties depending on position of carbon atoms and their percentages. Our results show that only when one carbon atom is situated on the edge of the nanowire, C-doped BNNW is transformed into half-metal. The calculated electronic structure of the C-doped BNNW suggests that doping carbon can induce localized edge states around the Fermi level, and the interaction among localized edge states leads to semiconductor to half-metal transition. Overall, the bond reconstruction causes of appearance of different electronic behavior such as semiconducting, half-metallicity, nonmagnetic metallic, and ferromagnetic metallic characters. The formation energy of the system shows that when a C atom is doped on surface boron site, system is more stable than the other positions of carbon impurity. Our calculations show that C-doped BNNW may offer unique opportunities for developing nanoscale spintronic materials. [ABSTRACT FROM AUTHOR]

The spin-polarized first-principles calculations are performed to study the electronic structures and magnetic properties of a single or double identical transition metal (TM) atoms X (X = Mn, Fe, Co and Ni) doped monolayer WS 2 systems. Although the pristine monolayer WS 2 system is a nonmagnetic semiconductor with a direct band gap of 1.820 eV, a single Mn, Fe, Co or Ni doped WS 2 systems exhibit the magnetic half-metallic (HM) characters with the total magnetic moments M tot of 1, 2, 3 and 4 μ B and the smaller spin-down gaps E g of 1.262, 1.154, 1.407 and 1.073 eV, respectively. For double identical TM atoms doped monolayer WS 2 systems, except for the cases of two Ni atoms doped at the first (0,1), second (0,2) and third (0,3) nearest-neighbor cation configuration which are antiferromagnetic (AFM), ferromagnetic (FM) and FM metals, respectively, the other cases are all HM ferromagnets, and the total magnetic moment M tot increases not only for double identical TM dopants Mn, Fe, Co and Ni (except for (0,1) AFM case) successively at the same nearest-neighbor cation configuration but also for each of the double identical TM dopants at the first (0,1), second (0,2) and third (0,3) nearest-neighbor cation configurations successively. These results provide a theoretical guide to choose new two-dimensional HM ferromagnetic materials in spintronic applications. [ABSTRACT FROM AUTHOR]

By using the Green’s functions method and linear response theory we calculate the shear viscosity of a two-component dipolar Fermi gas with population imbalance (spin polarized) in the low temperatures limit. In the strong-coupling Bose–Einstein condensation (BEC) region where a Feshbach resonance gives rise to tightly bound dimer molecules, a spin-polarized Fermi superfluid reduces to a simple Bose–Fermi mixture of Bose-condensed dimers and the leftover unpaired fermions (atoms). The interactions between dimer–atom, dimer–dimer, and atom–atom take into account to the viscous relaxation time ( τ η ) . By evaluating the self-energies in the ladder approximation we determine the relaxation times due to dimer–atom ( τ D A ) , dimer–dimer ( τ c D D , τ d D D ) , and atom–atom ( τ A A ) interactions. We will show that relaxation rates due to these interactions τ D A − 1 , τ c D D − 1 , τ d D D − 1 , and τ A A − 1 have T 2 , T 4 , e − E / k B T ( E is the spectrum of the dimer atoms), and T 3 / 2 behavior respectively in the low temperature limit ( T → 0 ) and consequently, the atom–atom interaction plays the dominant role in the shear viscosity in this rang of temperatures. For small polarization ( τ D A , τ A A ≫ τ c D D , τ d D D ), the low temperatures shear viscosity is determined by contact interaction between dimers and the shear viscosity varies as T − 5 which has the same behavior as the viscosity of other superfluid systems such as superfluid neutron stars, and liquid helium. [ABSTRACT FROM AUTHOR]

Conventional multidimensional magic angle spinning (MAS) solid-state NMR (ssNMR) experiments detect the signal arising from the decay of a single coherence transfer pathway (FID), resulting in one spectrum per acquisition time. Recently, we introduced two new strategies, namely DUMAS ( DU al acquisition M agic A ngle S pinning) and MEIOSIS ( M ultiple E xper I ments via O rphan S p I n operator S ), that enable the simultaneous acquisitions of multidimensional ssNMR experiments using multiple coherence transfer pathways. Here, we combined the main elements of DUMAS and MEIOSIS to harness both orphan spin operators and residual polarization and increase the number of simultaneous acquisitions. We show that it is possible to acquire up to eight two-dimensional experiments using four acquisition periods per each scan. This new suite of pulse sequences, called MAeSTOSO for M ultiple A cquisitions via S equential T ransfer of O rphan S pin p O larization, relies on residual polarization of both 13 C and 15 N pathways and combines low- and high-sensitivity experiments into a single pulse sequence using one receiver and commercial ssNMR probes. The acquisition of multiple experiments does not affect the sensitivity of the main experiment; rather it recovers the lost coherences that are discarded, resulting in a significant gain in experimental time. Both merits and limitations of this approach are discussed. [ABSTRACT FROM AUTHOR]

We study spin and valley transport through a ferromagnetic/nonmagnetic/ferromagnetic (FNF) monolayer silicene junction in the presence of an electrostatic gate potential U and on-site potential difference Δ z in the nonmagnetic region. We theoretically demonstrate that away from the band gap (no spin and valley conductances), the spin and valley polarizations of the junction show an oscillatory behaviour with U but near to it, they almost show a linear dependence with U. These oscillations are due to the phase difference of the electron wavefunctions of the spin and valley-resolved conductances that lead to chiral nature of the quasi-bound states in silicene. In particular, we find that the amplitude and frequency of the spin and valley polarizations oscillations of the junction can be tuned by varying the electrostatic gate potential U and on-site potential difference Δ z . Furthermore, it is shown that by increasing the exchange energy h the amplitudes of the spin and valley polarizations oscillations suppress. Enhanced spin (valley) polarization and its control by means of the electrostatic gate potential U makes the nonmagnetic tunneling junction a suitable candidate for utilizing in valleytronics and spintronics applications. [ABSTRACT FROM AUTHOR]

Dissolution-DNP is a method to create solutions of molecules with nuclear spin polarization close to unity. The many orders of magnitude signal enhancement have enabled many new applications, in particular in vivo MR metabolic imaging. The method relies on solid state dynamic nuclear polarization at low temperature followed by a dissolution to produce the room temperature solution of highly polarized spins. This work describes the present and future of dissolution-DNP in the mind of the author. The article describes some of the current trends in the field as well as outlines some of the areas where new ideas will make an impact. Most certainly, the future will take unpredicted directions, but hopefully the thoughts presented here will stimulate new ideas that can further advance the field. [ABSTRACT FROM AUTHOR]

We discuss the polarization dynamics during solid effect dynamic nuclear polarization (DNP) in a central spin model that consists of an electron surrounded by many nuclei. To this end we use a recently developed formalism and validate first its performance by comparing its predictions to results obtained by solving the Liouville von Neumann master equation. The use of a Monte Carlo method in our formalism makes it possible to significantly increase the number of spins considered in the model system. We then analyse the dependence of the nuclear bulk polarization on the presence of nuclei in the vicinity of the electron and demonstrate that increasing the minimal distance between nuclei and electrons leads to a rise of the nuclear bulk polarization. These observations have implications for the design of radicals that can lead to improved values of nuclear spin polarization. Furthermore, we discuss the potential to extend our formalism to more complex spin systems such as cross effect DNP. [ABSTRACT FROM AUTHOR]

Room temperature optical illumination of NV− imbibed single crystal diamonds with a 532 nm laser produces 13 C polarization enhancements up to 200 times greater than that of the thermal equilibrium value at 7.05 T. We report high field NV− mediated 13 C polarization as a function of the number and type (NV− and P1) of defects in commercially available diamonds. Surprisingly, both positive and negative 13 C polarizations are observed depending on the orientation of the crystal with respect to the external magnetic field and the electric field vector of the optical illumination. The data reported herein cannot be explained by a previously proposed mechanism. [ABSTRACT FROM AUTHOR]

In this work, we have investigated transport and optical properties of n-i-n resonant tunneling diodes (RTDs) containing a layer of InAs self-assembled quantum dots (QDs) grown on a (311)B oriented GaAs substrate. Polarization-resolved photoluminescence (PL) and magneto-transport measurements were performed under applied voltage and magnetic fields up to 15 T at 2 K under linearly polarized laser excitation. It was observed that the QD circular polarization degree depends strongly on the applied voltage. Its voltage dependence is explained by the formation of excitonic complexes such as positively (X + ) and negatively (X − ) charged excitons in the QDs. Our results demonstrate an effective electrical control of an ensemble of InAs QD properties by tuning the applied voltage across a RTD device into the resonant tunneling condition. [ABSTRACT FROM AUTHOR]

Fe/Mn single atomic layer with b.c.c structure is coherently inserted into half-Heusler compound CoTiSb. Electronic structures, magnetic properties and interface effects of the CoTiSb/Fe(Mn)/CoTiSb superlattice have been investigated by using the first-principles calculations. We predicted that a conductive film with 100% spin polarization is formed by the single atomic layer of Fe/Mn as the center between the semiconductor CoTiSb. And the single atomic layer of Fe/Mn has a limited influence on the electronic structures of the atomic layers inside CoTiSb. These make the CoTiSb/Fe(Mn)/CoTiSb superlattice a potential candidate for spintronic device, such as TMR, etc. [ABSTRACT FROM AUTHOR]

We study the spin-dependent shot noise properties in magnetic graphene superlattice with Rashba spin–orbit interaction (RSOI). The magnetic field generated by N parallel ferromagnets (FM) deposited on a dielectric layer. We consider two types of magnetic profiles: the FM stripes with magnetization parallel ( P ) or antiparallel ( AP ) perpendicular to the graphene. It is found that the shot noise of a spin state can be efficiently controlled by the number of barrier, RSOI strength and magnetic field. In the first case the Fano factor shows a peak with value approximately F = 1/3 for the both spin-up and spin-down electrons at new Dirac-like point. The position of the new Dirac point is robust against the magnetic field and RSOI. In the second case the Fano factor increases by increasing the number of barriers, and plateau of the Fano factor is formed. The results indicate that there is a strong relationship between spin-dependent shot noise and the magnitude of the spin polarization. [ABSTRACT FROM AUTHOR]