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The current-induced magnetization switching (CIMS) was successfully observed in epitaxial L10-FePt/CrxPt1−x (0 ≤ x ≤ 1) heterostructures grown by molecular beam epitaxy with large perpendicular magnetic anisotropy. With increasing Cr content, the critical switching current density (Jc) in FePt/CrxPt1−x heterostructures exhibited a decreasing trend, where it was greatly reduced by 69% in FePt/Cr (3d) films compared to FePt/Pt (5d) films with strong spin–orbit coupling. Furthermore, the same switching polarities were observed for all FePt/CrxPt1−x samples, indicating that the orbital Hall effect played a dominant role in CIMS for FePt/Cr films because of opposite spin Hall angles for Cr and Pt. Our results will put forward the applications of L10-FePt in collaboration with the orbital Hall effect from 3d metals in current-controlled magnetic random access memory and neuromorphic computing. [ABSTRACT FROM AUTHOR]

The formation mechanism of non-recessed Au–free Ohmic contacts on the AlGaN/GaN heterostructures is investigated for various Ti/Al atomic ratios (Al–rich versus Ti–rich) and annealing temperatures ranging from 500 to 950 °C. It is shown that Ti/Al atomic ratio is the key parameter defining the optimum annealing temperature for Ohmic contact formation. Ti–rich contacts processed at high temperature result in low contact resistance ∼0.7 Ω mm, better to those obtained at low temperature or with Al–rich metal stacks. The variation of the contact resistance with Ti/Al atomic ratio and annealing temperature is correlated with the intermetallic phase changes and interfacial reaction. Depending on the Ti/Al atomic ratio, two distinct mechanisms can be distinguished. For a small quantity of Ti (e.g., Al–rich contacts), Ohmic contact formation is done through a weak interfacial reaction which is nonexistent at high temperature due to the degradation of the metal morphology. However, for a quantity of Ti higher than 25 at. % (e.g., Ti–rich contacts), the agglomeration is delayed by 200 °C as compared to Al–rich contacts, and optimal contacts are formed at high temperature through a strong interfacial reaction. [ABSTRACT FROM AUTHOR]

By constructing dynamic equations including electrons, holes and their pair densities, we calculate the magnetoconductance (MC) and the magnetoelectroluminescence (MEL) separately. It is indicated that MC and MEL may result from different response on the applied magnetic field. MC is from the scattering of polarons by magnetic field related triplet excitons, while MEL is mainly from magnetic field related conversion between singlet and triplet electron-hole pairs. Furthermore, we discuss the relation between MC and MEL. The theoretical calculations are well consistent with the experimental results. [ABSTRACT FROM AUTHOR]

The mechanism of structural transition in nanocrystalline metals was studied from a thermodynamic point of view. Crystal lattice distortion and interfacial effect were found to be the reasons for structural instability. Nanocrystalline Fe samples prepared by the milling method and by the crystallization method were used for analyses and comparison. The contributions of lattice distortion and interfacial energy to thermodynamics were calculated using the quasiharmonic Debye approximation and the Gibbs-Thomson equation, respectively. By examining the change in Gibbs free energy and considering the effect of negative stress of grain boundaries on the crystal volume change in structural transition, we calculated the critical grain size of fcc-Fe formation. Results show that relative to the crystallized nanocrystalline state, it is more likely that the fcc Fe forms in the milled nanocrystalline state. Whether or not the phase transition occurs in nanocrystalline materials is closely related to the preparation technology, the grain-boundary structure, and the grain size. [ABSTRACT FROM AUTHOR]

The effect of combined Cu and Ti additions on the magnetic properties and phase transformation behavior of Nd[sub 8]Fe[sub 86]B[sub 6] nanocomposites prepared by melt spinning have been investigated. For pure ternary Nd[sub 8]Fe[sub 86]B[sub 6] ribbons, the α-Fe phase precipitates directly from amorphous phase and its grains grow quickly during crystallization. But for Nd[sub 8]Fe[sub 86]B[sub 6] ribbons with a combined addition of Cu and Ti, the crystallization temperature is increased by about 30 °C and a metastable hexagonal phase with a TbCu[sub 7]-type structure is formed prior to the α-Fe and Nd[sub 2]Fe[sub 14]B phase. When the annealing temperature is increased, a metastable 1:7 phase is decomposed into the α-Fe and Nd[sub 2]Fe[sub 14]B phase. At the same time, the growth of α-Fe grains is suppressed and the microstructure becomes more uniform. When the content of Cu reaches 1.0 at. % and that of Ti reaches 0.5 at. %, the optimal magnetic properties [sub i]H[sub c] = 4.8 kOe, σ[sub r] = 110 emu/g, (BH)[sub max] = 15 MGOe were obtained after annealing at the temperature of 650 °C for 8 min. So, a combined addition of Cu and Ti is very effective in improving the magnetic properties and reducing grain size and, in particular, the size of α-Fe grains. [ABSTRACT FROM AUTHOR]

Hall and resistivity measurements as functions of temperature were used to study the segregation of phosphorus in atmospheric-pressure chemical-vapor deposited, ∼300-nm-thick, polycrystalline Si[sub 0.95]Ge[sub 0.5] and Si[sub 0.9]Ge[sub 0.1] thin films, implanted at 80 keV with 6 × 10[sup 13] - 5 × 10[sup 14] P/cm², and annealed for 1 h at 800°C. Hall measurements, feasible only in heavily doped films, indicated that 29% of the dopant in Si[sub 0.9]Ge[sub 0.1] and 42% of the dopant in Si[sub 0.95]Ge[sub 0.05] were electrically inactive. The loss is consistent with dopant segregation to grain boundaries. The density of grain-boundary carrier traps is 3.6 × 10[sup 12]/cm² in Si[sub 0.95]Ge[sub 0.05] and 4.4 × 10[sup 12]/cm² in Si[sub 0.9]Ge[sub 0.1], increasing sublinearly with Ge content. [ABSTRACT FROM AUTHOR]

The grain-size reduction induced lattice distortion and its effect on crystal structural instability are analyzed. A criterion is proposed for determining the possible grain-size limit below which the amorphization has occurred.

Proposes a coupling model of the pluralistic magnetic component rare earth-transition metal intermetallic compounds. Types of interactions for rare-earth-transition-metal intermetallics; Calculation of the Curie temperature of the compounds; Features of the model for calculating temperature of the pluralistic compounds.

Room-temperature 1.54 μm electroluminescence (EL) was compared for Au/SiO[sub 2]:Er/n[sup +]-Si and Au/SiO[sub x]:Si:Er/n[sup +]-Si diodes under reverse bias. The 18 nm thick SiO[sub 2]:Er and SiO[sub x]:Si:Er films were deposited by the magnetron sputtering technique. The maximum of the EL intensity was reached after annealing at 900 °C (SiO[sub 2]:Er) and 800 °C (SiO[sub x]:Si:Er). The threshold potential of the EL was about 4 and 6 V for the Au/SiO[sub x]:Si:Er/n[sup +]-Si and Au/SiO[sub 2]:Er/n[sup +]-Si diodes, respectively. The power efficiency was larger for the Au/SiO[sub x]:Si:Er/n[sup +]-Si diode than that for the Au/SiO[sub 2]:Er/n[sup +]-Si diode by six times. Our experimental results demonstrate that the existence of Si nanoclusters reduces the threshold potentials of the EL and strongly enhances the power efficiency for Er[sup 3+] EL. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]