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We have investigated the anomalous Ettingshausen effect (AEE) in iron–carbon alloys, i.e., cast irons and steel, using the lock-in thermography. All the alloys exhibit the clear AEE-induced temperature modulation, and their anomalous Ettingshausen coefficient is an order of magnitude greater than that of the pure iron at room temperature. The dimensionless figure of merit for AEE in the ductile cast iron is 55 times greater than that in the pure iron owing to the significant increase in the anomalous Ettingshausen coefficient. Our result reveals a potential of iron–carbon alloys as transverse thermoelectric materials, although the composition and microstructures optimizations are necessary. [ABSTRACT FROM AUTHOR]

Ferrous medium-entropy alloys (FeMEAs) are coming into attention these days for their excellent mechanical properties. Most of the FeMEAs developed so far form metastable face-centered cubic (FCC) matrix, and "metastability engineering" that utilizes deformation-induced martensitic transformation (DIMT) from FCC to body-centered cubic (BCC) as a method to enhance work hardenability has been the key to the exceptional mechanical behaviors. However, the FeMEAs have a significant weakness: low yield strength compared with high tensile strength and ductility. In this study, partial recrystallization is presented as a solution to the current drawback of the FeMEAs. A Co18.5Cr12Fe55Ni9Mo3.5C2 (at. %) FeMEA was annealed at 800 °C for 10 and 30 min and partially recrystallized microstructures with relatively coarse non-recrystallized grains that contain profuse mechanical twins and ultrafine recrystallized grains were attained. In addition, nanosized Cr-rich M23C6-type and Mo-rich M6C-type carbides were precipitated during the annealing. The partially recrystallized FeMEA showed a yield strength of ∼1.07 GPa, significantly enhanced from ∼600 MPa of the recrystallized counterpart. Dislocation strengthening, precipitation strengthening, grain boundary strengthening, and twin boundary strengthening led to the improved strength of the partially recrystallized FeMEA. Back stress hardening owing to the heterogeneity also contributed to the high strength and work hardenability. Moreover, the transformation-induced plasticity effect from the FCC-to-BCC DIMT activated by BCC nucleation at defects within the non-recrystallized grains effectively enhanced the work hardenability, leading to ∼1.34 GPa of tensile strength and ∼30% of elongation. This study provides an insight to optimize the microstructure and corresponding mechanical properties of metastable metallic materials. [ABSTRACT FROM AUTHOR]

We report a chemically disordered solid solution, Al0.6Cr0.2MnFe0.5Co0.3Ni0.5, based on a body-centered cubic underlying lattice with the measured Curie temperature of ∼380 K. First-principles alloy theory is employed to investigate the temperature-dependent free energy, elastic constants, and coefficient of thermal expansion at the ferromagnetic and paramagnetic states. Theory and experiment are found to strengthen each other, and the results indicate that the magnetic state has a strong impact on the thermo-elastic properties of the considered alloy. The present advance in the thermo-magneto-elasticity enhances the understanding required for controlling the magnetic and mechanical response of multi-component systems. [ABSTRACT FROM AUTHOR]

We report the enhanced dielectric properties of iron atomically dispersed on nanocarbon. Theoretical simulations and calculations based on the Havriliak-Negami model and the first principles demonstrate that the increased dielectric property can be explained by the increased electrical conductivity and dielectric relaxations caused by the introduction of single iron atoms. Nanocarbon with single iron atoms exhibited enhanced electromagnetic wave absorption properties and could be further improved when being coupled with reduced graphene oxide. Our findings open a way for exploring high-performance materials with single metal atoms for practical applications in electromagnetic fields. [ABSTRACT FROM AUTHOR]

We have investigated magnesium aluminum ferrite thin films with a range of iron concentrations and identified the optimal iron content to obtain high crystalline quality thin films with the low magnetic damping required for spin current-based applications. Epitaxial MgAl 2 − x FexO4 films with 0.8 < x < 2.0 were grown by pulsed laser deposition on single crystal MgAl2O4 substrates and were characterized structurally and magnetically. We find that the x = 1.5 composition minimizes the room-temperature magnetic damping with a typical Gilbert damping parameter of α eff = 1.8 × 10 − 3 . This minimized damping is governed by a competition between the more robust magnetic ordering with increased iron content, x, and the more defective structure due to larger film-substrate lattice mismatch with increased iron content. The temperature-dependent magnetization curves indicate that Tc is suppressed below room temperature for iron content x ≤ 1.2 and eventually suppressed entirely for x = 0.8. X-ray magnetic circular dichroism results indicate that for all x the magnetic moment is dominated by Fe 3 + cations distributed in a 60:40 ratio on the octahedral and tetrahedral sites, with minimal contribution from Fe 2 + cations. Films with x = 1.4 − 1.6 exhibit very strong ferromagnetic resonance and low Gilbert damping with α eff = (1.8 − 6) × 10 − 3 , making them ideal candidates for microwave and spintronic applications. [ABSTRACT FROM AUTHOR]

We present a spintronic terahertz emitter based on a ferrimagnetic gadolinium-iron alloy (GdxFe1−x) and platinum (Pt). We measure the magnetic-field-dependent terahertz emission of GdxFe1−x/Pt spintronic heterostructures in the entire composition range (0 ≤ x ≤ 1). Excellent agreement is found between the measured data and a theoretical model based on the ratio of in-plane and saturation magnetization, up to a Gd content of x = 0.4 for all applied fields. At a higher Gd content (x ≥ 0.6), the measured terahertz amplitudes and the model deviate, due to the increasing influence of Gd. The GdxFe1−x/Pt emitters share similar properties with TbxFe1−x/Pt emitters, such as a strong increase in terahertz emission for a small rare earth content. However, our systematic study demonstrates that the terahertz emission amplitude of GdxFe1−x/Pt is up to 17 times higher than that of TbxFe1−x/Pt, which is important for the use and further optimization of these spintronic emitters operating at room temperature. [ABSTRACT FROM AUTHOR]

We report on the determination of the anomalous spin Hall angle in the ferromagnetic metal alloy cobalt-iron (Co25Fe75, CoFe). This is accomplished by measuring the spin injection/detection efficiency in a multiterminal device with nanowires of platinum (Pt) and CoFe deposited onto the magnetic insulator yttrium iron garnet (Y3Fe5O12, YIG). Applying a spin-resistor model to our multiterminal spin transport data, we determine the magnon conductivity in YIG, the spin conductance at the YIG/CoFe interface, and finally the anomalous spin Hall angle of CoFe as a function of its spin diffusion length in a single device. Our experiments clearly reveal a negative anomalous spin Hall angle of the ferromagnetic metal CoFe, but a vanishing ordinary spin Hall angle. This work, therefore, adds new observations to the results reported in Tian et al. [Phys. Rev. B 94, 020403 (2016)] and Das et al. [Phys. Rev. B 96, 220408(R) (2017)] , where the authors found finite contributions of the ordinary spin Hall angle in the ferromagnetic metals Co and Permalloy. [ABSTRACT FROM AUTHOR]

Satisfying the mutually conflicting requirements of easy switchability and high thermal stability still remains a hindrance to achieving ultra-high areal densities in hard disk drives. Exchange coupled composite media used with proper exchange control layers (ECLs) presents a potential solution to circumvent this hindrance. In this work, we have studied the role of MgO and Ta ECLs of different thicknesses in reducing the switching field of FePt media. MgO ECL was found to be more effective than a Ta ECL. For a 2 nm MgO ECL, the switching field could be reduced by 41% and at the cost of only a limited loss in thermal stability. Furthermore, a very high switching efficiency of 1.9 was obtained using 2 nm MgO ECL. So, with a proper choice of ECL material and thickness, the switching field of FePt media can be substantially reduced while ensuring high thermal stability and a better signal-to-noise ratio, thus potentially paving the way for very high areal density media. [ABSTRACT FROM AUTHOR]

The results of a study on the suitability of Fe-Ga alloys for torque sensor applications are presented. A Fe81Ga19 rod with a <100> preferred orientation along the length direction is prepared for the torque shaft and as the electromagnetic induction sensitive element, which is wound with three coils for signal excitation, signal pickup, and applied bias magnetic field, respectively. An apparent decrease in the induced voltage signal (peak voltage) of 3.88mV is observed as the torque loading is 50Nm in the presence of a sine excitation signal (10 V, 1 kHz) and a bias current of 0.5 A. Meanwhile, a good repeatability and stress sensitivity are obtained, especially in the low torque range. These behaviors stem from the stress induced decrease in the magnetic permeability and the rotation of the arranged magnetic moment. Here, we use the Fe81Ga19 alloy as the shaft material; nevertheless, in practical use, the same effect can be achieved by forming a Fe-Ga layer with large magnetostriction on the surface of the torsion shaft. This work shows the prospect of Fe-Ga alloys for non-contact torque sensing, for the large magnetostriction and high sensitivity of magnetization to stress. [ABSTRACT FROM AUTHOR]

We report an investigation of temperature dependent spin Hall magnetoresistance (SMR) and anisotropic magnetoresistance (AMR) in Ta/CoFe2O4 nanostructures. The AMR of the Ta/CoFe2O4 nanostructure starts to appear at 50K and its magnitude enhances dramatically with the decrease in temperature due to the suppressed spin-flip scattering. However, the SMR shows a complex temperature dependence correlated with the thickness of Ta layers. It increases monotonically and slightly with the decrease in temperature in thicker (7 nm) Ta. Moreover, Ta/CoFe2O4 nanostructures with thinner (3 nm) Ta exhibit a significant peak of SMR at about 75 K, probably owing to a good matching between the Ta layer thickness and its spin diffusion length. The fundamental distinct temperature dependences reveal different transport mechanisms of the two magnetoresistance effects. Our results will contribute to the further understanding and optimization of the magnetoresistance effects in spinel magnetic insulator heterojunctions. [ABSTRACT FROM AUTHOR]

We show that properly engineered amorphous Fe-Gd alloy thin films with perpendicular magnetic anisotropy exhibit bound pairs of like-polarity, opposite helicity skyrmions at room temperature. Magnetic mirror symmetry planes present in the stripe phase, instead of chiral exchange, determine the internal skyrmion structure and the net achirality of the skyrmion phase. Our study shows that stripe domain engineering in amorphous alloy thin films may enable the creation of skyrmion phases with technologically desirable properties. [ABSTRACT FROM AUTHOR]

The random substitution of a non-magnetic species instead of Fe atoms in FePt-L10 bulk alloy will permit to tune the magnetic anisotropy energy of this material. We have performed by means of first principles calculations a study of Fe1–yMnyPt-L10 (y=0.0, 0.08, 0.12, 0.17, 0.22, and 0.25) bulk alloy for a fixed Pt concentration when the Mn species have ferro-/antiferromagnetic (FM,AFM) alignment at the same(different) atomic plane(s). This substitution will promote several in-plane lattice values for a fixed amount of Mn. Charge hybridization will change compared to the FePt-L10 bulk due to this lattice variation leading to a site resolved magnetic moment modification. We demonstrate that this translates into a total magnetic anisotropy reduction for the AFM phase and an enhancement for the FM alignment. Several geometric configurations were taken into account for a fixed Mn concentration because of different possible Mn positions in the simulation cell. [ABSTRACT FROM AUTHOR]

We experimentally observed the inverse spin Hall effect (ISHE) of ferromagnetic FePt alloys. Spin Seebeck effect due to the temperature gradient generated the spin current (Js) in the FePt|Y3Fe5O12 (YIG) structure, and Js was injected from YIG to FePt and converted to the charge current through ISHE of FePt. The significant difference in magnetization switching fields for FePt and YIG led to the clear separation of the voltage of ISHE from that of anomalous Nernst effect in FePt. We also investigated the effect of ordering of FePt crystal structure on the magnitude of ISHE voltage in FePt. [ABSTRACT FROM AUTHOR]

We investigated the upper critical fields of Ca10(Pt4As8)(Fe1.8Pt0.2As2)5 superconducting whiskers. The whiskers consist of several wire-like grains with diameter of around 200 nm, joined by grain boundaries whose misorientation angles are less than 5°. The upper critical fields along c-axis and in ab-plane were observed as 49 T at 12K and 50 T at 22K, respectively, which can be extrapolated to 81 and ~133 T at 0 K. The whisker demonstrated weak anisotropic factor and almost constant value of ~2 below 15 K. The impressive transport properties of the whisker may find applications in fields like superconducting micro- and meso-structure systems. [ABSTRACT FROM AUTHOR]

The linear reversal mechanism in FePt grains ranging from 2.316 nm to 5.404 nm has been simulated using atomistic spin dynamics, parametrized from ab-initio calculations. The Curie temperature and the critical temperature (T*), at which the linear reversal mechanism occurs, are observed to decrease with system size whilst the temperature window T* < T < TC increases. The reversal paths close to the Curie temperature have been calculated, showing that for decreasing system size the reversal path becomes more elliptic at lower temperatures, consistent with the decrease in the Curie temperature arising from finite size effects. Calculations of the minimum pulse duration show faster switching in small grains and are qualitatively described by the Landau-Lifshitz-Bloch equation with finite size atomistic parameterization, which suggests that multiscale modeling of FePt down to a grain size of ≈3:5 nm is possible. [ABSTRACT FROM AUTHOR]

We prepare the high quality epitaxial MgO(001)[100]/Pt(001)[100]/NiO(001)[100]/FeNi/SiO2 films to investigate the spin transport in the NiO antiferromagnetic insulator. The ferromagnetic resonance measurements of the FeNi under a spin current injection from the Pt by the spin Hall effect revealed the change of the ferromagnetic resonance linewidth depending on the amount of the spin current injection. The results can be interpreted that there is an angular momentum transfer through the NiO. A high efficient angular momentum transfer we observed in the epitaxial NiO can be attributed to the well-defined orientation of the antiferromagnetic moments and the spin quantization axis of the injected spin current. [ABSTRACT FROM AUTHOR]

Magnetostrictive FeGa thin films were deposited on the bowed flexible polyethylene terephthalate (PET) substrates, which were fixed on the convex mold. A compressive stress was induced in FeGa films when the PET substrates were shaped from convex to flat. Due to the effect of magnetostriction, FeGa films exhibit an obvious in-plane uniaxial magnetic anisotropy which could be enhanced by increasing the applied pre-strains on the substrates during growth. Consequently, the ferromagnetic resonance frequency of the films was significantly increased, but the corresponding initial permeability was decreased. Moreover, the films with pre-strains less than 0.78% exhibit a working bandwidth of microwave absorption about 2GHz. Our investigations demonstrated a convenient method via the prestrained substrates to tune the high frequency properties of magnetic thin films which could be applied in flexible microwave devices. [ABSTRACT FROM AUTHOR]

The magnetic state of the FeMnP0.75Si0.25 alloy was investigated by first principles calculations. The coexistence of ferromagnetic and antiferromagnetic phases in FeMnP0.75Si0.25 with the same hexagonal crystal structure was revealed. It was found that kinetic arrest during the transition from the high temperature disordered paramagnetic phase to the low temperature ordered ferromagnetic phase results in the intermediate metastable and partially disordered antiferromagnetic phase. We propose that the ratio of the ferromagnetic and antiferromagnetic phases in the FeMnP0.75Si0.25 sample can be tuned by adjusting the kinetic process of atomic diffusion. The investigations suggest that careful control of the kinetic diffusion process provides another tuning parameter to design candidate magnetocaloric materials. [ABSTRACT FROM AUTHOR]

Interface perpendicular magnetic anisotropy (PMA) in ultrathin Fe/MgO (001) has been investigated using angular-dependent x-ray magnetic circular dichroism (XMCD). We found that anisotropic orbital magnetic moments deduced from the analysis of XMCD contribute to the large PMA energies, whose values depend on the annealing temperature. The large PMA energies determined from magnetization measurements are related to those estimated from the XMCD and the anisotropic orbital magnetic moments through the spin-orbit interaction. The enhancement of anisotropic orbital magnetic moments can be explained mainly by the hybridization between the Fe 3dz2 and O 2pz states. [ABSTRACT FROM AUTHOR]

Friction is a ubiquitous phenomenon in everyday activities spanning from vehicles where efficient brakes are mandatory up to mechanical devices where its minimum effects are pursued for energy efficiency issues. Recently, theoretical models succeed correlating the friction behavior with energy transference via phonons between sliding surfaces. Therefore, considering that the energy losses by friction are prompted through phonons, the chemical surface structure between sliding surfaces is very important to determine the friction phenomenon. In this work, we address the issue of friction between a conical diamond tip sliding on different functionalized flat steel surfaces by focusing the influence of the chemical bonds in the outermost layers on the sliding resistance. This geometry allows probing the coupling of the sharp tip with terminator species on the top and underneath material surface at in-depth friction measurements from 20 to 200 nm. Experimentally, the friction coefficient decreases when nitrogen atoms are substituted for oxygen in the iron network. This effect is interpreted as due to energy losses through phonons whilst lower vibrational frequency excitation modes imply lower friction coefficients and a more accurate adjustment is obtained when a theoretical model with longitudinal adsorbate vibration is used. [ABSTRACT FROM AUTHOR]

Herein, we report the emergence of intrinsic multicolor photoluminescence in Fe2O3 nanoparticles (NPs) ranging from blue, cyan, to green, upon facile functionalization and further surface modification with a small organic ligand, Na-tartrate. Moreover, we have found unprecedented photocatalytic property of the functionalized Fe2O3 NPs in the degradation of a model water-contaminant. Meticulous investigation through UV-visible absorption and fluorescence study along with theoretical support from literature unfolds that ligand-to-metal charge-transfer transition from the tartrate ligand to the lowest unoccupied energy level of Fe3+ of the NPs and d-d transitions centered over Fe3+ ions in the NPs play the key role in the emergence of multiple photoluminescence from the ligand functionalized Fe2O3 NPs. Moreover, vibrating sample magnetometry measurements demonstrate that the surface modification changes the magnetic behaviour of Fe2O3 NPs upon functionalization. We believe that the great potential of our versatile, ferromagnetic, multicolor photoluminescent Fe2O3 NPs would stimulate the development of numerous opportunities toward their biological and technological applications. [ABSTRACT FROM AUTHOR]

An Fe3Pt alloy with degree of order 0.75 exhibits a second-order-like martensitic transformation from a cubic structure to a tetragonal one at about 90 K; its tetragonality c/a changes nearly continuously from 1 to 0.945 on cooling from 90K to 14 K. We have investigated the change in lattice parameters in a single crystal of the Fe3Pt alloy at 93K under compressive stresses, σ, applied in the [001] direction by neutron diffraction. The tetragonality c/a has decreased continuously from 1 to 0.907 with an increase in |σ| up to |σ|=280MPa; the corresponding lattice strain in the [001] direction, due to the continuous structure change, increases from 0% to 6.1%. When the stress of 300MPa is reached, c/a has changed abruptly from 0.907 to 0.789 due to a first-order martensitic transformation. [ABSTRACT FROM AUTHOR]

The microstructures of SmFeAs(O,F), Ba(Fe,Co)2As2, and FeTe0.5Se0.5 prepared on CaF2 substrates were investigated using transmission electron microscopy. The SmFeAs(O,F)/CaF2 interface is steep, without a disordered layer. By contrast, a chemical reaction occurs at the interface in the cases of Ba(Fe,Co)2As2 and FeTe0.5Se0.5. The reaction layers are located on opposite sides of the interface for Ba(Fe,Co)2As2 and FeTe0.5Se0.5. We found that the lattice distortion of the three superconducting films on the CaF2 substrates enhances the TC values compared with films prepared on oxide substrates. The origin of this lattice deformation varies depending on the superconducting material. [ABSTRACT FROM AUTHOR]

We report the magnetic field and stress tunable microwave behaviour of microwire-epoxy composites containing Fe-based microwires of different lengths. Observation of a crossover magnetic field at 600Oe, when the wire length is less than 35mm, is reasoned to be related to the competition between giant magnetoimpedance and ferromagnetic resonance in addition to the wire's intrinsic properties. Samples containing 25mm microwires exhibit a linear increase of the permittivity tunability as the tensile strain is increased up to 2.0%. This can be attributed to the longitudinal anisotropy field and the wire alignment under strain. [ABSTRACT FROM AUTHOR]

The microstructures of SmFeAs(O,F), Ba(Fe,Co)2As2, and FeTe0.5Se0.5 prepared on CaF2 substrates were investigated using transmission electron microscopy. The SmFeAs(O,F)/CaF2 interface is steep, without a disordered layer. By contrast, a chemical reaction occurs at the interface in the cases of Ba(Fe,Co)2As2 and FeTe0.5Se0.5. The reaction layers are located on opposite sides of the interface for Ba(Fe,Co)2As2 and FeTe0.5Se0.5. We found that the lattice distortion of the three superconducting films on the CaF2 substrates enhances the TC values compared with films prepared on oxide substrates. The origin of this lattice deformation varies depending on the superconducting material. [ABSTRACT FROM AUTHOR]

A five-phase laminate composite transducer based on nanocrystalline soft magnetic FeCuNbSiB alloy is presented, whose magnetoelectric (ME) coupling characteristics have been investigated. It is found that the resonant ME voltage coefficient of FeCuNbSiB/Terfenol-D/Pb(Zr1-x,Tix)O3 (PZT)/Terfenol-D/FeCuNbSiB (FMPMF) five-phase transducer is much larger than that of traditional Terfenol-D/PZT/Terfenol-D (MPM) transducer, resulting from the enhancement of the effective mechanical quality factor and effective piezomagnetic coefficient of the transducers. Appropriate FeCuNbSiB layer thickness is propitious to the resonant and low-frequency ME coupling characteristics. The maximum resonant ME voltage coefficient achieves 4.81 V/Oe with FeCuNbSiB layer thickness is 60 μm under the DC bias magnetic field Hb=77 Oe, which is 1.48 times as great as that of traditional MPM transducer. In addition, the maximum ME voltage coefficient at low frequency is 51.2 mV/Oe under the DC bias magnetic field Hb=442 Oe, which is 1.26 times as great as that of traditional MPM transducer. It indicates that the mentioned five-phase laminate composite transducers have great potential for the application of highly sensitive dc magnetic field sensing and vibration energy harvesting. [ABSTRACT FROM AUTHOR]

The Fe1-xVx alloy system exhibits the lowest known Gilbert relaxation rate of any ferromagnetic metal or binary alloy with G = 35 MHz at x = 27% V. Low relaxation rates are of particular interest in modern spin electronic applications involving spin torque. The transport spin polarization of a series of sputtered epitaxial Fe1-xVx samples was measured using point contact Andreev reflection. Values of the transport spin polarization agree well with those measured for pure Fe and are independent of composition. The results indicate that the substitution of up to 50% of V for Fe does not reduce the spin polarization in the alloy. [ABSTRACT FROM AUTHOR]

Melt spun ribbon of Fe73Ga27 was prepared and characterized for microstructural features and magnetostriction. The phase equilibria observed from structural investigations have been correlated with Mossbauer studies. The magnetostriction of the melt spun ribbon has been found to be significantly large compared to the bulk sample. The large magnetostriction is attributed to the absence of ordered fcc (L12) phase in the melt spun ribbon, which is otherwise seen in slow cooled bulk Fe73Ga27 alloy. [ABSTRACT FROM AUTHOR]

TiN was investigated as a potential spacer material in L10-FePt based pseudo spin valves (PSV). PSVs with the structure MgO/L10-Fe50Pt50 (20 nm)/TiN (5 nm)/L10-Fe50Pt50 (x nm) were fabricated, where x was varied from 5 to 20 nm. The highest giant magnetoresistance (GMR) ratio of 0.61% was obtained for the PSV with a top L10-FePt thickness of 20 nm. Contributions to the GMR arose from both the spin dependent scattering at the FePt/TiN interfaces and domain wall resistivity. Magnon magnetoresistance was also observed in the fabricated PSVs. [ABSTRACT FROM AUTHOR]

We report the realization of grain alignment in Sn-added Sr1-xKxFe2As2 superconducting tapes with Fe sheath prepared by ex-situ powder-in-tube method. At 4.2 K, high transport critical current densities Jc of 2.5 × 104 A/cm2 (Ic = 180 A) in self-field and 3.5 × 103 A/cm2 (Ic = 25.5 A) in 10 T have been measured. These values are the highest ever reported so far for Fe-based superconducting wires and tapes. We believe the superior Jc in our tape samples are due to well textured grains and strengthened intergrain coupling achieved by Sn addition. Our results demonstrated an encouraging prospect for application of iron based superconductors. [ABSTRACT FROM AUTHOR]

In this work, the tetragonal-phase BaTiO3 high dielectric (HK) layer and the magnetic FePt metal gate (MG) film are proposed to be the gate stack scheme on the Ge three dimensional (3D) n-type multi-gate-field-effect transistors (FETs). The ~75% dielectric constant (j-value) improvement, ~100× gate leakage (Jg) reduction, and ~70% on-state current (Ion) enhancement are achieved due to the colossal magneto-capacitance effect. The magnetic field from the magnetic FePt MG film couples and triggers more dipoles in the BaTiO3 HK layer and then results in the super gate stack characteristics. The promising transistor's performance (~200 lA/lm on the device with the gate length Lch=60 nm) on the high mobility (Ge) material in the 3D n-type multi-gate-FETs device structure demonstrated in this work provides the useful solution for the future advanced logic device design. [ABSTRACT FROM AUTHOR]

We present a fully integrated microelectromechanical magnetic field sensor based on the ΔE effect. The vacuum encapsulated sensor extends our previous approach [B. Gojdka et al., Appl. Phys. Lett. 99, 223502 (2011); Nature 480, 155 (2011)] and now involves an intermediate piezoelectric AlN layer between a SiO2 cantilever and a magnetostrictive FeCoBSi top layer. The AlN layer serves two functions: It drives the resonator, and it is used for electrical read out. The limit of detection was strongly enhanced to 12 nT/√Hz at 10 Hz. [ABSTRACT FROM AUTHOR]

Thermoelectric elements that were formed from vertically aligned microspheres were fabricated from 500-µm monosized spherical particles of Fe2VAl alloys with a particle assembly that used pulsed current micro-welding. P-n pairs of the elements consisting of three particles generated relatively large temperature differences ΔT despite being 1.5 mm tall. At ΔT = 19 K, the five pairs generated a voltage of 21 mV and a maximum generation power of 40 µW, which converted to 0.21 V/cm2 voltage per unit area and 0.4 mW/cm2 power density, respectively. Moreover, we demonstrated the feasibility of building a massive array with 100 elements. [ABSTRACT FROM AUTHOR]

Superconducting thin films of SmFeAs(O,F) were prepared by molecular beam epitaxy on fluoride substrates. In our process, F-free SmFeAsO films were grown first, and F was subsequently introduced to the films by diffusion from an overlayer of SmF3. By this simple process, record high Tc, namely, Tcon (Tcend) = 57.8 K (56.4 K) was obtained in a film on CaF2. Furthermore, the films on CaF2 showed high critical current density over 1 MA/cm2 in the self-field at 5 K. The correlation between superconductivity and epitaxial strain in SmFeAs(O,F) films is discussed. [ABSTRACT FROM AUTHOR]

Based on the spin-pumping theory and first-principles calculations, the spin-mixing conductance (SMC) is theoretically studied for Pt/Permalloy (Ni81Fe19, Py) junctions. We evaluate the SMC for ideally clean Pt/Py junctions and examine the effects of interface randomness. We find that the SMC is generally enhanced in the presence of interface roughness as compared to the ideally clean junctions. Our estimated SMC is in good quantitative agreement with the recent experiment for Pt/Py junctions. We propose possible routes to increase the SMC in Pt/Py junctions by depositing a foreign magnetic metal layer in Pt, offering guidelines for designing the future spintronic devices. [ABSTRACT FROM AUTHOR]

The interlayer coupling effects in L10-FePt based pseudo spin valve were investigated through the reversal behavior and exchange bias properties of the soft L10-FePt layer. The magnitude and sign of the exchange bias field were highly dependent on the magnetization state of the hard L10-FePt layer. In the presence of a fully saturated hard L10-FePt layer, the exchange bias effect stemmed from interlayer interactions due to possible pinholes, Ruderman-Kittel-Kasuya-Yosida or Néel coupling. With a partially saturated hard L10-FePt layer, stray fields emanated from the domain walls of the nonuniformly magnetized hard L10-FePt layer also contributed to the overall coupling strength. [ABSTRACT FROM AUTHOR]

We report the use of an ultralow noise nano-superconducting quantum interference device (nanoSQUID) to measure the hysteretic magnetization behavior of a single FePt nanobead at a temperature of around 7 K in a magnetic field of only ∼10 mT. We also show that the nanobead can be accurately positioned with respect to the SQUID loop and then removed without affecting SQUID performance. This system is capable of further development with wide applications in nanomagnetism. [ABSTRACT FROM AUTHOR]

We have investigated the ultrafast magnetization dynamics of L10-ordered Fe50Pt50 thin film by means of a time-resolved magneto-optical Kerr effect measurement. We have found a high Gilbert damping value of α∼0.26, together with a very high precession frequency of f∼85 GHz and the shortest relaxation characteristic time of τ∼6.5 ps ever reported. We believe that L10-ordered FePt film with the unique property of a very high precession frequency and the shortest relaxation time will be very useful for the realization of picosecond spin switching. [ABSTRACT FROM AUTHOR]

Using the density functional calculations, we investigated the effect of nanoprecipitation on the magnetostriction of Fe1-xGax alloys. While the B2-like FeGa clusters undergo slight tetragonal distortion, D03-like FeGa clusters remain cubic in the Fe matrix. Moreover, we found that B2-like nanostructures produce negative magnetostriction, whereas D03-like nanostructures give small positive magnetostriction in the hypothetical inhomogeneous structures. Therefore, the formation of nanoscale precipitates cannot be the reason for the extraordinary enhancement of magnetostriction of Fe1-xGax alloys. [ABSTRACT FROM AUTHOR]

A heterostructured Fe71Si15Ti10Cu4 ultrafine composite has been developed. The addition of Cu with large positive enthalpy of mixing with the main constituent element (Fe) leads to evolution of a unique microstructure with different length-scale heterogeneities, i.e., formation of spherical colonies containing length-scale heterogeneity of lamellar spacing and precipitation of nanoscale multitwinned Cu within α-Fe layers. These macroscopic and microscopic structural heterogeneities are able to simultaneously achieve high strength and plasticity, together with pronounced work hardening by avoiding the deformation instability. [ABSTRACT FROM AUTHOR]

This paper reports the observation of the clear Invar effects of (Fe71.2B24Y4.8)96Nb4 bulk metallic glass. The Invar effects of (Fe71.2B24Y4.8)96Nb4 alloys in different structural states are also investigated in situ through cyclic thermal dilation tests at different cyclic temperatures. The results show that these Invar effects are strengthened in the relaxation amorphous state, weakened in the nanocrystalline state, and absent in the complete crystalline state. X-ray diffraction and Mössbauer spectroscopy demonstrate that the structural influences on Invar effects can be explained by the different local atomic arrangements around Fe atoms in different structural states. [ABSTRACT FROM AUTHOR]

Doping FePt nanoparticles could be a possible approach to achieve high L10 order and magnetic anisotropy. To address stability, first-principles studies of surface segregation of dilute Ag/Au/Cu solutes at and near the (001)/(100)/(111) surfaces of FePt-L10 are performed. It is found that a strong surface segregation tendency at first outer layer is present in all the cases. For Cu, segregation is less than half of Ag and Au. Ag and Cu segregate to Fe sites at surfaces and preferentially substitute for Fe in the bulk, whereas Au substitutes for Fe at surfaces and for Fe and Pt in the bulk. [ABSTRACT FROM AUTHOR]

Doping FePt nanoparticles could be a possible approach to achieve high L10 order and magnetic anisotropy. To address stability, first-principles studies of surface segregation of dilute Ag/Au/Cu solutes at and near the (001)/(100)/(111) surfaces of FePt-L10 are performed. It is found that a strong surface segregation tendency at first outer layer is present in all the cases. For Cu, segregation is less than half of Ag and Au. Ag and Cu segregate to Fe sites at surfaces and preferentially substitute for Fe in the bulk, whereas Au substitutes for Fe at surfaces and for Fe and Pt in the bulk. [ABSTRACT FROM AUTHOR]

The reversal mechanisms of graded anisotropy FePtCu films have been investigated by alternating gradient magnetometer (AGM) and magneto-optical Kerr effect (MOKE) measurements with first-order reversal curve (FORC) techniques. The AGM-FORC analysis, which clearly shows the presence of soft and hard components, is unable to resolve how these phases are distributed throughout the film thickness. MOKE-FORC measurements, which preferentially probe the surface of the film, reveal that the soft components are indeed located toward the top surface. Combining AGM-FORC with the inherent surface sensitivity of MOKE-FORC analysis allows for a comprehensive analysis of heterogeneous systems such as graded materials. [ABSTRACT FROM AUTHOR]

We have investigated the feasibility of using FePdB alloy layers for perpendicular magnetic tunnel junctions (p-MTJs). The perpendicular magnetic anisotropy (PMA) of FePdB films is obtained by depositing amorphous Fe40Pd40B20 layers on proper templates and by postannealing. An FePdB film on a thick Pt (001) underlayer has a PMA energy (Ku) of 4.9×106 erg/cm3, and an FePdB layer sandwiched by two thin MgO (001) layers shows a Ku of 3.7×106 erg/cm3. A double barrier p-MTJ with an FePdB middle layer shows a tunnel magnetoresistance of 6.8%. [ABSTRACT FROM AUTHOR]

Using a micromagnetics calculation, we explore the properties of a submicron magnetic square with microwave assisted switching. For a 10×160×160 nm3 structure of Fe-Ti-N, there are three particular stable magnetic states for reversal fields up to -320 Oe. One can switch between these different states by adding a microwave field. The strength and the frequency of the microwave field determine the final state. A microwave field of up to 30 Oe does not change the magnetization. Fields of 50 to 75 Oe result in an intermediate state, while larger microwave fields produce a reversed ground state. [ABSTRACT FROM AUTHOR]

Ru1-xFex alloys crystallize in a hexagonal-close-packed structure for x<0.70 with a space group of P63/mmc, the same phase as that of a high pressure phase of iron, [variant_greek_epsilon]-Fe. Thermal expansion coefficients of Ru1-xFex alloys of various compositions were determined over a temperature range of 300–530 K using high resolution x-ray diffraction measurements. The coefficients of linear thermal expansion for hexagonal phase along the c and a axes showed a linear dependence on the composition. These results when extrapolated showed direct relationship to the thermoelastic properties of [variant_greek_epsilon]-Fe. This study also demonstrates that high pressure and high temperature phases can be simulated and engineered to exist at ambient conditions with proper choice of alloying. [ABSTRACT FROM AUTHOR]

Lorentz microscopy was applied to the observation of magnetic domains in iron-gallium (Fe–Ga) alloys. Results did not show any link between the magnetic domains and the magnetostriction enhancement by Ga addition, but did reveal that the drastic decrease in magnetostriction for Fe–31.2 at. % Ga was due to the presence of large scale precipitates. Magnetic domain features did not change in the alloys of A2, D03, A2+D03, A2+B2+D03, and A2+fine scale precipitates. Large scale precipitates within the slow-cooled Fe–31.2 at. % Ga affected both the distribution and wall motion of magnetic domains. [ABSTRACT FROM AUTHOR]

An exchange-coupled FePt/Fe3Pt nanocomposite system with well defined hard/soft two-phase morphology was prepared by reducing chemically synthesized FePt/Fe3O4 bimagnetic nanoparticles. It was interesting to observe that the recoil loop openness is strongly dependent on the sweep rate of applied fields. A quantitative analysis shows a linear relation between the openness of recoil loops and the reciprocal activation volume, indicating that the recoil loops are intimately related to thermal fluctuation. The large open area of the recoil loops for nanocomposite magnets compared to that of single phase magnets is attributed to the unstable magnetic moments in the soft phase. [ABSTRACT FROM AUTHOR]

We have evaluated the lifetime and diffusion length of photogenerated minority carriers (holes) in single-crystalline n-type β-FeSi2 bulk grown by chemical vapor transport. The diffusion length measured by optical-beam-induced current agreed well with that measured by electron-beam-induced current, that is, 51 and 38 μm, respectively, for samples annealed at 800 °C for 8 h. The decay curve of photoconductivity obtained by 1.31 and 1.55 μm light pulses was well fitted by assuming a carrier lifetime of approximately a few microseconds. The mobility of photogenerated minority carriers was estimated to be approximately 200–360 cm2/V s from the measured lifetime and diffusion length. [ABSTRACT FROM AUTHOR]