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In this report, hematene (2D α-Fe2O3 nanosheets) with an exceptionally high coercivity of up to 7.5 kOe has been synthesized via a soft-chemical exfoliation process. The high coercivity correlates with the surface magnetic anisotropy that originates from enhanced uncompensated spin canting as a result of the 2D morphology. This observation is different from the behavior of the bulk counterpart that exhibits collinear antiferromagnetic ordering with no net magnetization at low temperatures. In addition, our study shows a suppression of the Morin transition in 2D nanosheets, which further confirms that the surface spins deviate strongly from the collinear antiferromagnetic ordering. We also observed a spin-glass-like transition with a rapid increase in saturation magnetization and a decrease in anisotropy in the ultra-thin α-Fe2O3 nanosheets at temperatures below 48 K. The spin-glass behavior is correlated with the observed exchange bias and the magnetic field dependence of spin-glass freezing temperature. [ABSTRACT FROM AUTHOR]

We report the electrical detection of multiple ferromagnetic (FM) resonance modes in multilayers of Pt/Fe20Ni80/Ru/Fe20Ni80 using microwave spin pumping and the inverse spin Hall effect (ISHE) as a function of Ru layer thickness tRu. The electrically detected voltage signals were analyzed for the anti-parallel magnetization state as well as the "spin-flop" magnetization state of the two Fe20Ni80 layers. When the two FM layers are antiferromagnetically (AFM) coupled (tRu = 1 nm), both the optic and acoustic modes were observed. The amplitude of the acoustic mode voltage signals obtained increases with frequency. However, when the two magnetic layers are ferromagnetically coupled (tRu = 1.4 nm), only acoustic mode was observed whose voltage signals decreases as frequency increases. We demonstrate the tunability of the sign of the ISHE voltage in the AFM coupled system by controlling the polarization of the spin currents. [ABSTRACT FROM AUTHOR]

The recently discovered thermally induced magnetization switching (TIMS) induced by single femtosecond laser pulses in ferrimagnetic GdFeCo alloys proceeds on the picosecond time-scale. The rate at which data can be changed for use of TIMS in technological devices is limited by the processes leading to thermal equilibrium. In the present work, we address the question of whether it is possible to further excite switching via TIMS well before thermal equilibrium between subsystems is reached. In particular, we investigate the conditions for double thermally induced magnetic switching by the application of two shortly delayed laser pulses. These conditions become relevant for potential applications as it sets both a limit to rewrite data and demonstrates the importance of spatial confinement of a heat pulse to bit size, as neighboring bits may be accidentally re-switched for spatially extended pulse spots. To demonstrate this effect, we theoretically study the switching behavior in a prototypical ferrimagnetic GdFeCo alloy as a function of composition. We use computer simulations based on thermal atomistic spin dynamics and demonstrate the possibility of inducing a second switching event well before thermal equilibrium is reached and define the conditions under which it can occur. Our theoretical findings could serve as a guidance for further understanding of TIMS as well as to act as a guide for future applications. [ABSTRACT FROM AUTHOR]

We measure linear absorption, circular dichroism, second harmonic, and sum frequency generation in the [Δ-Fe(phen)3](Δ-As2(tartarate)2), [Λ-Fe(phen)3](Λ-As2(tartarate)2) enantiomers of an Fe(II) complex. In the solid state, the chirality of this compound results from the introduction of the (As2(tartarate)2) chiral anions. Linear absorption and X-ray diffraction indicate that Fe(II) is in the low-spin state. Circular dichroïsm reveals that in the solid state, these compounds are chiral, whereas the complexes racemize in solution. A large second harmonic generation signal is recorded using thin films from these two enantiomers. The second-order susceptibility χ111(2) of these compounds is evaluated across the visible spectral range. It displays a resonance at 520 nm, which is associated with the metal-to-ligand charge transfer occurring within the complex. At its maximum, χ111(2) = 6.4 pm V-1 is more than 1.4 times larger than the well-known beta-BaB2O4 nonlinear crystal (χ122(2) ~4.4 pm V-1). Finally, we demonstrate a useful application for a thin film from this compound, which characterizes the cross-correlation of two femtosecond laser pulses. [ABSTRACT FROM AUTHOR]

Metal-insulator transition features as a transformation from a highly charge conductive state to another state where the charge conductivity is greatly suppressed when decreasing the temperature. Here, we demonstrate two consecutive transitions in NdNiO3 films with CoFe2O4 capping, in which the metal-insulator transition occurs at ~85 K, followed by an unprecedented insulatormetal transition below 40 K. The emerging insulator-metal transition associated with a weak antiferromagnetic behavior is observed in 20 unit cell-thick NdNiO3 with more than 5 unit cell CoFe2O4 capping. Differently, the NdNiO3 films with thinner CoFe2O4 capping only exhibit metalinsulator transition at ~85 K, accompanied by a strong antiferromagnetic state below 40 K. Charge transfer from Co to Ni, instead of from Fe to Ni, formulates the ferromagnetic interaction between Ni-Ni and Ni-Co atoms, thus suppressing the antiferromagnetic feature and producing a metallic conductive behavior. Furthermore, a phase diagram for the metal-insulator-metal transition in this system is drawn. [ABSTRACT FROM AUTHOR]

Metal-insulator transition features as a transformation from a highly charge conductive state to another state where the charge conductivity is greatly suppressed when decreasing the temperature. Here, we demonstrate two consecutive transitions in NdNiO3 films with CoFe2O4 capping, in which the metal-insulator transition occurs at ~85 K, followed by an unprecedented insulatormetal transition below 40 K. The emerging insulator-metal transition associated with a weak antiferromagnetic behavior is observed in 20 unit cell-thick NdNiO3 with more than 5 unit cell CoFe2O4 capping. Differently, the NdNiO3 films with thinner CoFe2O4 capping only exhibit metalinsulator transition at ~85 K, accompanied by a strong antiferromagnetic state below 40 K. Charge transfer from Co to Ni, instead of from Fe to Ni, formulates the ferromagnetic interaction between Ni-Ni and Ni-Co atoms, thus suppressing the antiferromagnetic feature and producing a metallic conductive behavior. Furthermore, a phase diagram for the metal-insulator-metal transition in this system is drawn. [ABSTRACT FROM AUTHOR]

We present direct measurements of the magnetocaloric effect on a Fe2P-based compound induced by a milliseconds pulsed magnetic field of 1 T to test their possible use in high frequency (up to 100 Hz) thermomagnetic cycles. The reported measurements were performed with an innovative and versatile non-contact set up based on the mirage effect. The adiabatic temperature change of a MnFeP0.45As0.55 sample is presented and compared with measurements performed varying the same magnetic field in a time interval of 1 s and 100 ms. These results demonstrate the absence of kinetic constraints in the first-order phase transition of this sample induced on the milliseconds time scale. The study of the materials' response to millisecond magnetic field pulses represents a fundamental test for the development of more powerful and efficient magnetic refrigerators. [ABSTRACT FROM AUTHOR]

An unexplained surfaceanisotropy effect was observed and confirmed in the magnetization reversal process of both L10 phase FePt nanoparticles with octahedral shape and (001) textured L10 FePt thin films with island nanostructures. We suggest that the nature of the observed surface effect is caused by broken symmetry on the FePt surface, which results in weakened exchange coupling for surface atoms. Furthermore, we propose, and experimentally demonstrate, a method to repair the broken symmetry by capping the FePt islands with a Pt layer, which could prove invaluable in understanding fundamental limitations of magnetic nanostructures. [ABSTRACT FROM AUTHOR]

Thickness modulation at the edges of nanostructured magnetic thin films is shown to have important effects on their perpendicular magnetic anisotropy. Thin film wires with tapered edges were made from [Co/Pd]20 multilayers or L10-FePt films using liftoff with a double-layer resist. The effect of edge taper on the reversal process was studied using magnetic force microscopy and micromagnetic modeling. In [Co/Pd]20, the anisotropy was lower in the tapered edge regions which switched at a lower reverse field compared to the center of the wire. The L10-FePt wires showed opposite behavior with the tapered regions exhibiting higher anisotropy. [ABSTRACT FROM AUTHOR]

Ferromagnet/semiconductor heterostructure, such as Fe/GaAs, is always one of the key issues in spintronics due to its prerequisite for the realization of spin sensitive devices. In this letter, a lateral photoelectric effect (LPE) was observed in Fe/GaAs. Our results show that the sensitivity was not related to laser wavelength, but only proportional to laser power, suggesting that the lateral photovoltage was induced by photo-thermo-electric effect. Moreover, we also observe that the voltage signal increases with the increase in applied field due to decreasing scattering probability for spin-polarized electrons. Our finding of LPE adds another functionality to the Fe/GaAs system and will be useful in development of spin-polarized voltage devices. [ABSTRACT FROM AUTHOR]

The 2-dimensional transformation of the diamond (111) surface to graphene has been demonstrated using ultrathin Fe films that catalytically reduce the reaction temperature needed for the conversion of sp³ to sp² carbon. An epitaxial system is formed, which involves the re-crystallization of carbon at the Fe/vacuum interface and that enables the controlled growth of monolayer and multilayer graphene films. In order to study the initial stages of single and multilayer graphene growth, real time monitoring of the system was preformed within a photoemission and low energy electron microscope. It was found that the initial graphene growth occurred at temperatures as low as 500 °C, whilst increasing the temperature to 560 °C was required to produce multi-layer graphene of high structural quality. Angle resolved photoelectron spectroscopy was used to study the electronic properties of the grown material, where a graphene-like energy momentum dispersion was observed. The Dirac point for the first layer is located at 2.5 eV below the Fermi level, indicating an n-type doping of the graphene due to substrate interactions, while that of the second graphene layer lies close to the Fermi level. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate a prototype of magnetic tunable bandstop filter by using magnetic multilayers of [FeGaB 25 nm/Al2O3 5 nm]4 prepared by magnetron sputtering. The multilayer structure exhibits a relatively low coercive field and RF loss compared to the single layer film with the same thickness. By placing a single transmission line on the top of magnetic multilayers, a prototype of tunable bandstop filter was fabricated and operates from 4.5 GHz to 7.08 GHz under very low magnetic bias fields from 100 Oe to 400 Oe. These low loss multilayer films are good candidates for RF/microwave applications. [ABSTRACT FROM AUTHOR]

B2-ordered FeRh has been known to exhibit antiferromagnetic-ferromagnetic (AF-F) phase transitions in the vicinity of room temperature. Manipulation of the Néel order via AF-F phase transition and recent experimental observation of the anisotropic magnetoresistance in antiferromagnetic FeRh has proven that FeRh is a promising candidate for antiferromagnetic memory material. In this work, we demonstrate sequential write and read operations in antiferromagnetic memory resistors made of B2-orderd FeRh thin films by a magnetic field and electric current only, which open a realistic pathway towards operational antiferromagnetic memory devices. [ABSTRACT FROM AUTHOR]

Single crystal ferromagnetic Fe3Si(111) films were grown epitaxially on GaAs(111)A by molecular beam epitaxy. These hetero-structures possess extremely low surface roughness of 1.3 Å and interfacial roughness of 1.9 Å, measured by in-situ scanning tunneling microscope and X-ray reflectivity analyses, respectively, showing superior film quality, comparing to those attained on GaAs(001) in previous publications. The atomically smooth interface was revealed by the atomic-resolution Z (atomic number)-contrast scanning transmission electron microscopy (STEM) images using the correction of spherical aberration (Cs)-corrected electron probe. Excellent crystallinity and perfect lattice match were both confirmed by high resolution x-ray diffraction. Measurements of magnetic property for the Fe3Si/GaAs(111) yielded a saturation moment of 990 emu/cm³ with a small coercive field ≤1 Oe at room temperature. [ABSTRACT FROM AUTHOR]

We presented a quantitative study on the Fe-doping concentration dependence of optical nonlinearities and ultrafast carrier dynamics in Fe-doped GaN (GaN:Fe) single crystals using picosecond Z-scan and femtosecond pump-probe with phase object techniques under two-photon excitation. In contrast to the two-photon absorption that was found to be independent on the Fe-doping, the nonlinear refraction decreased with the Fe concentration due to the fast carrier trapping effect of Fe3+/Fe2+ deep acceptors, which simultaneously acted as an efficient non-radiative recombination channels for excess carriers. Remarkably, compared to that of Si-doped GaN bulk crystal, the free-carrier refraction effect in GaN:Fe crystals was found to be enhanced considerably since Fe-doping and the effective carrier lifetime (~10 ps) could be tuned over three orders of magnitude at high Fe-doping level of 1 × 1019 cm-3. [ABSTRACT FROM AUTHOR]

The authors present a mid-IR depressed cladding waveguide laser in Fe:ZnSe. The laser produced a maximum output power of 76 mW at 4122 nm and laser thresholds as low as 154 mW were demonstrated. This represents a 44% reduction in threshold power compared with the bulk laser system demonstrated in this paper. The waveguide laser was found to have a narrow spectral linewidth of 6 nm FHWM compared to the 50 nm typical of bulk Fe:ZnSe lasers. [ABSTRACT FROM AUTHOR]

Interactions of hydrogen with iron have been studied in Fe contaminated p-type Czochralski silicon using capacitance-voltage profiling and deep level transient spectroscopy (DLTS). Hydrogen has been introduced into the samples from a silicon nitride layer grown by plasma enhanced chemical vapor deposition. After annealing of the Schottky diodes on Si:Fe + H samples under reverse bias in the temperature range of 90-120 °C, a trap has been observed in the DLTS spectra which we have assigned to a Fe-H complex. The trap is only observed when a high concentration of hydrogen is present in the near surface region. The trap concentration is higher in samples with a higher concentration of single interstitial Fe atoms. The defect has a deep donor level at Ev + 0.31 eV. Direct measurements of capture cross section of holes have shown that the capture cross section is not temperature dependent and its value is 5.2 × 10-17 cm². It is found from an isochronal annealing study that the Fe-H complex is not very stable and can be eliminated completely by annealing for 30 min at 125 °C. [ABSTRACT FROM AUTHOR]

Lorentzian-shaped broader three-terminal Hanle (B-3TH) signals are observed in Fe/SiO2/Si tunnel junction devices at 6-300 K. We propose a spin conducting model, which explains all the characteristics of our experimental results, such as field angle dependence and bias dependence of the B-3TH signals, as well as experimental results reported by other groups. It was found that the shape of the B- 3TH signals is determined by the spin depolarization at the Fe/SiO2 interface caused by local magnetic fields, unlike the conventional understanding. The shape of the B-3TH signals, including narrower and inverted Hanle signals, reflects the magnetic order of an ultrathin paramagnetic layer formed at the Fe/SiO2 interface. Our model provides a unified explanation of the B-3TH signals observed in threeterminal Hanle measurements. [ABSTRACT FROM AUTHOR]

The magnetic characteristics of dilute Fe-doped SrTiO3 ceramics are studied. The roomtemperature ferromagnetism (with transition temperature around 650 K) is successfully realized in Sr0.98Ti0.9Fe0.1O3-δ and Sr0.98Ti0.92Fe0.1O3-δ ceramics. It is found that a fine-tuning of the components could alter the substitution sites of Fe ions and in-turn modulates the magnetism of the material. A systematic analysis reveals that the co-substitution of Fe ions at nonequivalent A and B sites in ABO3 type perovskites is in favor of the ferromagnetism, which could be attributed to the mixed-valence-states of Fe ions and the variation of exchange interactions. This work provides an innovation for the induction and control of ferromagnetism in dilute magnetic materials. [ABSTRACT FROM AUTHOR]

The upper critical field Hc2 anisotropy of Ca10(PtnAs8)(Fe2-xPtxAs2)5 (n=3, 4) single crystals with long FeAs interlayer distance (d) was studied by angular dependent resistivity measurements. A scaling of the angular dependent resistivity was realized for both single crystals using the anisotropic Ginzburg-Landau (AGL) approach with an appropriate anisotropy parameter γ. The AGL scaling parameter γ increases with decreasing temperature and reaches a value of about 10 at 0.8Tc for both single crystals. These values are much larger than those of other iron-based superconductors (FeSCs). Remarkably, the values of γ² show an almost linear increase with the FeAs/FeSe interlayer distance d for FeSCs. Compared to cuprates, FeSCs are less anisotropic, indicating that two dimensionality of the superconductivity is intrinsically weak. [ABSTRACT FROM AUTHOR]

The structural, electronic, and magnetic properties of single layers of Iron Dichloride (FeCl2) were calculated using first principles calculations. We found that the 1T phase of the single layer FeCl2 is 0.17eV/unit cell more favorable than its 1H phase. The structural stability is confirmed by phonon calculations. We found that 1T-FeCl2 possess three Raman-active (130, 179, and 237 cm-1) and one infrared-active (279 cm-1) phonon branches. The electronic band dispersion of the 1T-FeCl2 is calculated using both gradient approximation of Perdew-Burke-Ernzerhof and DFT-HSE06 functionals. Both functionals reveal that the 1T-FeCl2 has a half-metallic ground state with a Curie temperature of 17 K. [ABSTRACT FROM AUTHOR]

The structural, electronic, and magnetic properties of single layers of Iron Dichloride (FeCl2) were calculated using first principles calculations. We found that the 1T phase of the single layer FeCl2 is 0.17eV/unit cell more favorable than its 1H phase. The structural stability is confirmed by phonon calculations. We found that 1T-FeCl2 possess three Raman-active (130, 179, and 237 cm-1) and one infrared-active (279 cm-1) phonon branches. The electronic band dispersion of the 1T-FeCl2 is calculated using both gradient approximation of Perdew-Burke-Ernzerhof and DFT-HSE06 functionals. Both functionals reveal that the 1T-FeCl2 has a half-metallic ground state with a Curie temperature of 17 K. [ABSTRACT FROM AUTHOR]

Conductivity in Fe7Pd3 is characterized by an anomalous increase when traversing the face-centered-cubic (fcc) austenite to face-centered-tetragonal (fct) martensite transition, contrary to most other conventional and ferromagnetic shape memory alloys. Experiments on molecular-beam-epitaxy-grown single crystals indicate a resistivity change of ≈20% during the transformation on top of a quadratic temperature dependence reaching up to room temperature. The physical foundations of residual resistivity changes along the full Bain path are addressed by a Kubo-Greenwood approach within the framework of density functional theory. To do so, a concept to reliably extract the DC conductivities is proposed that yields reproducible results consistent with experiments. Finding that conductivity peaks in the fct phase, we identify a large density of states paired with high velocities at the Fermi level in the majority spin sub-bands in presence of minimum s-d electron scattering as underlying physical origin. [ABSTRACT FROM AUTHOR]

A series of FePt films with different magnetic structures are deposited on Pb(Mg1/3Nb2/3)O3-PbTiO3 substrates. By applying an electric field across the piezoelectric single crystal substrate, an magnetoelectric effect is observed in FePt/Pb(Mg1/3Nb2/3)O3-PbTiO3 heterostructure due to the phase transformation between face-centered cubic and face-centered tetragonal phases in the film. Taking advantage of the different coercivity caused by the electric field, the sign of magnetization can be manipulated reversibly at room temperature with the electric field switching on or off. Based on this experimental result, we demonstrate a model for the technology of information storage, in which data can be written electrically without false writing. [ABSTRACT FROM AUTHOR]

Microstructurally clean, isovalently P-doped BaFe2As2 (Ba-122) single crystalline thin films have been prepared on MgO (001) substrates by molecular beam epitaxy. These films show a superconducting transition temperature (Tc) of over 30 K although P content is around 0.22, which is lower than the optimal one for single crystals (i.e., 0.33). The enhanced Tc at this doping level is attributed to the in-plane tensile strain. The strained film shows high transport self-field critical current densities (Jc) of over 6 MA/cm² at 4.2 K, which are among the highest for Fe based superconductors (FeSCs). In-field Jc exceeds 0.1 MA/cm² at μ0H = 35 T for H||ab and μ0H = 18 T for H||c at 4.2 K, respectively, in spite of moderate upper critical fields compared to other FeSCs with similar Tc. Structural investigations reveal no defects or misoriented grains pointing to strong pinning centers. We relate this unexpected high Jc to a strong enhancement of the vortex core energy at optimal Tc, driven by in-plane strain and doping. These unusually high Jc make P-doped Ba-122 very favorable for high-field magnet applications. [ABSTRACT FROM AUTHOR]

In-situ, time-resolved small-angle neutron scattering (SANS) investigations of the early stages of the spinodal decomposition process in Fe-35Cr were performed at 773 and 798 K. The kinetics of the decomposition, both in terms of characteristic distance and peak intensity, followed a power-law behaviour from the start of the heat treatment (a′ = 0.10-0.11 and a″ = 0.67-0.86). Furthermore, the method allows tracking of the high-Q slope, which is a sensitive measure of the early stages of decomposition. Ex-situ SANS and atom probe tomography were used to verify the results from the in-situ investigations. Finally, the in-situ measurement of the evolution of the characteristic distance at 773 K was compared with the predictions from the Cahn-Hilliard-Cook model, which showed good agreement with the experimental data (a′ = 0.12-0.20 depending on the assumed mobility). [ABSTRACT FROM AUTHOR]

Grain boundary junctions were fabricated in the epitaxial FeSe0.5Te0.5 thin films on [001] tilt SrTiO3 bi-crystal substrates with a CeO2 buffer layer. Critical current densities across the junctions with different mis-orientation angles of 4°, 7°, 15°, and 24° were measured at magnetic fields up to 30 T. It was found that the 4° and 7° junctions carry critical current densities comparable to that of the intra-grain film while those of the 15° and 24° junctions were suppressed drastically. A critical mis-orientation angle of around 9° was identified that separates the strong coupling region from the weak link region. We found that the critical current densities across the grain boundary with a 24° mis-orientation angle are modulated by the magnetic field, indicating a Josephson Effect. This junction is estimated to be in the intermediate-size regime with an effective transverse junction width L ~ 2.6-2.8 im and a Josephson penetration depth λ ~ 1.2 μm. [ABSTRACT FROM AUTHOR]

The thermal behavior of Fe as a compensating acceptor impurity in b-Ga2O3 (010) was studied in view of growing interests in semi-insulating Fe-doped Ga2O3 substrates for the realization of highperformance Ga2O3 field-effect transistors (FETs). An anomalous redistribution of Fe beyond the extent of intrinsic thermal diffusion was revealed by secondary ion mass spectroscopy in devicerelevant structures where Ga2O3 grown homoepitaxially on Fe-doped substrates was doped by Si ion (Si+) implantation and annealed at high temperatures. The enhanced Fe diffusion was attributed to an athermal process involving intrinsic defects from the region of implantation damage. An undoped Ga2O3 buffer between the Si+-implanted layer and the Fe-doped substrate effectively suppressed Fe outdiffusion by protecting the substrate against unintentional ion damage or defects from a remote source, thereby preserving the electrical integrity of the Si-doped material. Temperature-dependent current-voltage measurements indicated that the undoped Ga2O3 buffer was highly resistive with inter-device leakage attributable to surface conduction via a variablerange hopping mechanism. The buffer scheme, together with dielectric passivation to eliminate surface leakage, was proposed to constitute an integral process module for future lateral Ga2O3 FET devices. [ABSTRACT FROM AUTHOR]

This paper develops a self-biased magnetoelectric (ME) heterostructure FeCuNbSiB/Terfenol-D/ Be-bronze/Pb(Zr,Ti)O3 (PZT) by sandwiching a nonmagnetic elastic Be-bronze plate between an piezoelectric PZT plate and a magnetization-graded FeCuNbSiB/Terfenol-D layer. The Be-bronze plate severs as the resonance frequency determining element of the ME heterostructure. By using the magnetization-graded magnetostrictive layer and the elastic Be-bronze plate, seven large peaks of ME response with magnitudes of 0.3-10 (V/cm Oe) in 1-70 kHz range are observed at zerobiased magnetic field. This demonstrates that the proposed multi-peak self-biased heterostructure may be useful for multifunctional devices such as multi-frequency energy harvesters or lowfrequency ac magnetic field sensors. [ABSTRACT FROM AUTHOR]

We report room temperature giant baroresistance (≈128%) in Fe49(Rh0.93Pd0.07)51. With the application of external pressure (P) and magnetic field (H), the temperature range of giant baroresistance (≈600% at 5K, 19.9 kilobars and 8 T) and magnetoresistance (≈ ~85% at 5K and 8 T) can be tuned from 5 K to well above room temperature. It is shown that under external pressure, antiferromagnetic state is stabilized at room temperature and shows giant magnetoresistance (≈~55%). Due to coupled magnetic and lattice changes, the isothermal change in resistivity at room temperature under pressure (at constant H) as well as magnetic field (at constant P) can be scaled together to a single curve, when plotted as a function of X = T + 12.8 x H -- 7.3 x P. [ABSTRACT FROM AUTHOR]

This paper develops a self-biased magnetoelectric (ME) heterostructure FeCuNbSiB/Ni-PZTFeCuNbSiB/ Ni (FN-P-FN) by bonding magnetization-graded FeCuNbSiB/Ni layers at the free ends of piezoelectric Pb(Zr,Ti)O3 (PZT) plate. By using the magnetization-graded magnetostrictive layer and end-bonding heterostructure, giant self-biased ME responses and obvious hysteresis are observed in FN-P-FN heterostructure. The experimental results show that the zero-biased ME voltage coefficient of FN-P-FN heterostructure reaches ~183.2 (V/cm Oe), which is ~2.1, ~4.5, and ~41.6 times higher than that of FeCuNbSiB/Ni/PZT, Ni-PZT-Ni, and FeCuNbSiB-PZTFeCuNbSiB composites, respectively. The results indicate that the proposed three-phase end-bonding heterostructure shows promising applications for high-sensitivity self-biased magnetic field sensors and ME transducers. [ABSTRACT FROM AUTHOR]

An approach is presented that allows quantifying the three dimensional magnetization pattern of a magnetic nanoobject from measured two dimensional Magnetic Force Microscopy (MFM) data. This is based on a MFM deconvolution approach, which quantitatively determines the effective surface charges, on a micromagnetic calculation of the total magnetic charges at and below the sample surface, and on a projection of the lower lying charges onto the sample surface for a comparison of the such obtained effective surface charges with the experimentally determined ones. Thus, by making use of the depth sensitivity of MFM and by applying a quantitative contrast analysis, we are able to reconstruct the inhomogeneous magnetization state at the end of individual cylindrical Fe52Co48 nanowires arranged in a triangular array. As a result, we prove the existence of a magnetic vortex state at their ends. [ABSTRACT FROM AUTHOR]

We used in-situ potassium (K) evaporation to dope the surface of the iron-based superconductor FeTe0.55Se0.45. The systematic study of the bands near the Fermi level confirms that electrons are doped into the system, allowing us to tune the Fermi level of this material and to access otherwise unoccupied electronic states. In particular, we observe an electron band located above the Fermi level before doping that shares similarities with a small three-dimensional pocket observed in the cousin, heavily electron-doped KFe2-xSe2 compound. [ABSTRACT FROM AUTHOR]

Optical nonlinearities and transient dynamics of Fe doped GaN (GaN:Fe) were studied by Z-scan and pump-probe with phase object techniques under picosecond and nanosecond at 532 nm. From the pump-probe results, an additional decay pathway subsequent to two photon excitation was observed due to the carrier trapping of Fe3+/Fe2+ deep acceptors. The trapping state in the band gap results in a pronounced modulation to nonlinear responses of GaN:Fe compared to that of undoped GaN. With an effective three-level model as well as carrier trapping effect we described the photo-physical dynamics in GaN:Fe unambiguously. [ABSTRACT FROM AUTHOR]

A systematic study of LiFe2Cln (n = 4-6) clusters, based on gradient corrected density functional theory (DFT), shows that the electron contributed by Li can transform antiferromagnetic Fe2Cln (n = 4 and 6) clusters into ferromagnetic clusters. In Fe2Cl6 (Fe2Cl4) cluster, the Fe atoms in +3 (+2) oxidation states are aligned antiferromagnetically, consistent with the super-exchange model. The extra electron from Li atom creates a charge disproportionation in the LiFe2Cl6 (LiFe2Cl4) cluster that mediates the double-exchange interaction between the Fe atoms. Antiferromagnetic to ferromagnetic transition can also be induced by hole doping as seen to be the case with Fe2Cl5 which has a ferromagnetic ground state. Simultaneous electron and hole doping is also seen to impact on the magnetic properties of LiFe2Cl5 which can be viewed as (Fe2Cl4+LiCl). While Fe2Cl4 is antiferromagnetic and LiCl is nonmagnetic, the ground state of LiFe2Cl5 is ferromagnetic. We also analyzed the results with on-site Coulomb interaction U by performing DFT+U calculations. These results can be useful in the synthesis of functional molecular magnets. [ABSTRACT FROM AUTHOR]

We performed spin pumping experiment on high quality, epitaxial Fe3Si/GaAs structures grown by molecular beam epitaxy. By tailoring the thickness and doping (n, p) level of the conducting GaAs epi-layer, thermal heating common of ferromagnetic metal/semiconductor heterostructure was removed effectively. A large inverse spin Hall Effect (ISHE) voltage up to 49.2 μV was observed for Fe3Si/p-GaAs. Smaller ISHE voltage (VISHE) by a factor of ~0.4 was obtained for Fe3Si/n-GaAs, as scaled with its resistivity. By taking into account of the "self-induced" ISHE apparently observed in our samples, the minimum value of spin Hall angle ƟISHE for n-GaAs and p-GaAs was estimated tobe 1.9 x 10-4 and 2.8 x 10-5, respectively. [ABSTRACT FROM AUTHOR]

FeAlSi (Sendust) is known to possess excellent soft magnetic properties comparable to traditional soft magnetic alloys such as NiFe (Permalloy), while having a relatively higher resistance for lower eddy current losses. However, their dynamic magnetic and magneto-transport properties are not well-studied. Via the spin rectification effect, we electrically characterize a series of obliquely sputtered FeAlSi films at ferromagnetic resonance. The variations of the anisotropy fields and damping with oblique angle are extracted and discussed. In particular, two-magnon scattering is found to dominate the damping behavior at high oblique angles. An analysis of the results shows large anomalous Hall effect and anisotropic magneto-resistance across all samples, which decreases sharply with increasing oblique incidence [ABSTRACT FROM AUTHOR]

This letter reports the structural, dielectric, ferroelectric, and magnetic properties of Fe substituted SrTiO3 thin films in room temperature. The structural data obtained from x-ray diffraction indicates that (Fex,Sr1-x)TiO3, the so called FST, transforms from pseudocubic to tetragonal structures with increase of the Fe content in SrTiO3 thin films, featuring the ferroelectricity, while vibrating sample magnetometer measurements show magnetic hysteresis loops for the samples with low iron contents indicating their ferromagnetism. The characterized ferroelectricity and ferromagnetism confirms strong multiferroitism of the single phase FST thin films in room temperature. Also, an FST thin film metal-insulator-metal multiferroic capacitor has been fabricated and characterized in microwave frequencies between 10 MHz and 5 GHz. A capacitor based on Fe0.1Sr0.9TiO3 with a thickness of 260nm shows a high electric tunability of 18.6% at 10 V and a maximum magnetodi-electric value of 1.37% at 0.4 mT with a loss tangent of 0.021 at 1 GHz. This high tuning and low loss makes this material as a good candidate for frequency agile microwave devices such as tunable filters, phase shifters, and antennas [ABSTRACT FROM AUTHOR]

We have monitored the cathodoluminescence (CL) emitted upon injection of free electrons into a hybrid structure consisting of a thin magnetic Fe layer deposited on a p-GaAs substrate, in which InGaAs quantum wells are embedded. Electrons transmitted through the unbiased metal/ semiconductor junction recombine radiatively in the quantum wells. Because of the electron spinfiltering across the Fe/GaAs structure, the CL intensity, collected from the backside, is found to depend on the relative orientation between the injected electronic spin polarization and the Fe layer magnetization. The spin asymmetry of the CL intensity in such junction provides a compact optical method for measuring spin polarization of free electrons beams or of hot electrons in solid-state devices. [ABSTRACT FROM AUTHOR]

The multiferroic heterostructure of FeCoZr/[Pb(Mg1/3Nb2/3)O3]0.68-[PbTiO3]0.32(011) (PMN-PT) prepared by oblique sputtering deposition technique shows a large electrical tunability of ultra-high ferromagnetic resonance frequency from 7.4 GHz to 12.3 GHz. Moreover, we experimentally demonstrate the possibility of realizing electrically reconfigurable magnetoelectric microwave devices with ultra-low power consumption by employing the heterostructure under different resetting electric fields through a reconfiguration process. In particular, the tunability of the FeCoZr/PMN-PT heterostructure from 8.2 GHz to 11.6 GHz can retain in a remanent state after releasing the resetting electric field. This suggests that the tunable microwave devices based on such heterostructures are permanently reconfigurable by simply using a trigger electric field double-pulse which requires much less energy than that of the conventional ones wherein an electric field needs to be constantly applied during operation. [ABSTRACT FROM AUTHOR]

We investigated the Ag distribution in a FePtAg-C granular film that is under consideration for a heat assisted magnetic recording medium by aberration-corrected scanning transmission electron microscope-energy dispersive X-ray spectroscopy and X-ray absorption fine structure. Ag is rejected from the core of FePt grains during the deposition, forming Ag-enriched shell surrounding L10-ordered FePt grains. Since Ag has no solubility in both Fe and Pt, the rejection of Ag induces atomic diffusions thereby enhancing the kinetics of the L10-order in the FePt grains. [ABSTRACT FROM AUTHOR]

In order to increase the signal-to-noise ratio of heat assisted magnetic recording, it is desirable to fabricate high magnetic anisotropy FePt media with small grain size and high aspect ratio (grain height to size ratio). In the present paper, we report that FePt media with small grain size and high aspect ratio were achieved by doping ZrO2 into FePt film grown on TiON intermediate layer. The grain size was around 5.6 nm, and the aspect ratio was as high as 2.6. It is believed that this originated from the ZrO2 (002) tetragonal crystalline phase epitaxially grown on TiON intermediate layer. With a 5 vol. % carbon doping into FePt-ZrO2 films, the perpendicular anisotropy was improved and the out-of-plane coercivity was around 23.2 kOe. Doping of crystalline phase material with certain required crystal structure may offer a method for fabrication of nanostructured thin films with high aspect ratio grains at high processing temperature. [ABSTRACT FROM AUTHOR]

Heat assisted magnetic recording (HAMR) has been recognized as a leading technology to increase the data storage density of hard disk drives. Dispersions in the properties of the grains comprising the magnetic medium can lead to grain-to-grain Curie temperature variations, which drastically affect the jitter in the recorded magnetic transitions and limit the data storage density capabilities in HAMR. Here we present a method to measure the switching probability of an ensemble of exchange-decoupled grains with perpendicular anisotropy subject to nanosecond heating pulses. The short heat exposure time ensures that the grains switch by reaching the Curie temperature rather than through thermal activation. The switching probability can be directly interpreted as representing the Curie temperature distribution. The method is applied to two sets of samples to reveal the sensitivity of the Curie temperature distribution to FePt HAMR media fabrication parameters. This technique is of importance to engineer suitable HAMR media capable of high density magnetic recording and for fundamental studies on sources of magnetic disorder in granular magnetic media. [ABSTRACT FROM AUTHOR]

A mixed layer of γ-Fe2O3 and Pt-Fe2O3 core-shell nanoparticles between Ti and Pt electrodes exhibited both analog and digital bipolar resistive switching depending on applied voltage. The resistance sequentially reduced with repeated -1.5V sweeps and pulses for 100 ms and increased as repeating +1.5 V. After forming at +3V, digital bipolar switching was achieved with SET transition from high to low resistance at +1 to 2V and reverse RESET transition at -1V. Pulse operation at ±2V led to identical bipolar switching, associated with facilitated interconnection of filament segments between Pt cores in nanoparticle layer. [ABSTRACT FROM AUTHOR]

The converse magnetoelectric effect is studied by voltage tuning of magnetic resonance in a bilayer of (111) yttrium iron garnet (YIG) film and polycrystalline lead zirconate titanate (PZT) when the YIG film is in a multi-domain state or under magnetic saturation. The application of a DC voltage across PZT manifests as a uniaxial anisotropy field in YIG and results in a shift in the resonance. In the multi-domain state, the voltage tuning of resonance is strong with a magneto-electric coefficient A = 12 MHz cm/kV. Under magnetic saturation, the voltage tuning is rather weak with A = 2 MHz cm/kV. [ABSTRACT FROM AUTHOR]

In the superconductor of FeSe0.5Te0.5, the superconductivity is highly sensitive to variations of microstructure. Therefore, a fine manipulation of the microstructures will be crucial not only for a better understanding of the superconductivity but also for potential applications. Here, we demonstrate an approach to control the superconductivity in-situ by using a magnetostrictive substrate ZnCr2Se4 as the strain generator. By mounting an FeSe0.5Te0.5 single crystal onto a magnetostrictive substrate, we show that the magnetoresistance of FeSe0.5Te0.5 is directly coupled to the magnetostriction of ZnCr2Se4. The strain is fine-tuned in-situ by an external magnetic field, leading to the superconductivity of FeSe0.5Te0.5 correspondingly favored by compressive strain while suppressed by tensile strain. [ABSTRACT FROM AUTHOR]

In the superconductor of FeSe0.5Te0.5, the superconductivity is highly sensitive to variations of microstructure. Therefore, a fine manipulation of the microstructures will be crucial not only for a better understanding of the superconductivity but also for potential applications. Here, we demonstrate an approach to control the superconductivity in-situ by using a magnetostrictive substrate ZnCr2Se4 as the strain generator. By mounting an FeSe0.5Te0.5 single crystal onto a magnetostrictive substrate, we show that the magnetoresistance of FeSe0.5Te0.5 is directly coupled to the magnetostriction of ZnCr2Se4. The strain is fine-tuned in-situ by an external magnetic field, leading to the superconductivity of FeSe0.5Te0.5 correspondingly favored by compressive strain while suppressed by tensile strain. [ABSTRACT FROM AUTHOR]

We demonstrate that the direction of all-optical switching (AOS) in rare-earth transition-metal (RE-TM) alloy Tb-Fe thin films depends on the orientation of the sublattice magnetization and not on the direction of the resulting net magnetization. For this purpose, we investigated the AOS ability for a sample dominated by the Fe sublattice magnetization (Tb24Fe76) and another dominated by the Tb sublattice (Tb30Fe70). This finding of the sublattice dependence of AOS contributes to the understanding of switching in RE-TM multilayered thin films and heterostructures. [ABSTRACT FROM AUTHOR]

We report on structural and optical properties for the (0001)-oriented α-(CrxFe1-x)2O3 (0 ≤ x ≤ 1) epitaxial films prepared on c-sapphire substrates by using pulsed-laser deposition. Pure corundum phase with atomically flat surface was obtained in the entire composition range. Optical absorption spectra for the films with 0.2 < x < 0.9 showed a nearly constant band-gap (1.7 eV), which is narrower than those of α-Fe2O3 (2.1 eV) and α-Cr2O3 (3.0 eV). The result suggests that the band-gap narrowing arises from a type-II band alignment of these oxides and the fundamental band-gap lies between the Cr t2g and O 2p occupied states and the Fe t2g* empty state. [ABSTRACT FROM AUTHOR]

We present the magnetic/structural phase diagram of Sn1-xGaxCFe3 (0 ≤ x ≤ 1). With increasing x, Curie temperature (TC) and saturated magnetization increase while lattice constant decreases. The results indicate that GaCFe3 may be a promising high-temperature soft magnetic material. Around TC, chemical composition-dependent magnetocaloric effect is studied. The relative cooling power increases with increasing x, reaching a maximum of ∼3.22 J/cm3 (∼61% of Gd) around 345 K. Considering their remarkable advantages, Sn1-xGaxCFe3 are suggested to be promising magnetic refrigerant materials. The low-T resistivity displays a metallic behavior for x ≤ 0.80 and a semiconductor-like behavior for GaCFe3. Furthermore, room-temperature coefficient of resistivity is comparative (∼46.2 ppm/K for GaCFe3, 250-310 K). [ABSTRACT FROM AUTHOR]