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As-cast AlCrFeCoNiCu high-entropy alloy (HEA) was a solid solution of body-centered cubic (BCC) and face-centered cubic phases with a typical dendrite and interdendrite structures. The precipitated intermediate phases in 600°C annealed HEA are responsible for the improved hardness. After 1000°C annealing treatment, the crystalline was re-arranged because of the decomposition of BCC phases. The 1000°C annealed HEA has the best corrosion resistance due to its re-arranged crystalline structure. Meanwhile, the 600°C annealed HEA has the best erosion–corrosion resistance for its highest hardness and its wear rate is more than two times lower than that of AISI 304 stainless steel. Therefore, the HEA has a potential application in saline–sand slurry because of its superior corrosion and erosion–corrosion resistance.

Compound casting was used to achieve the joining of arc sprayed coating to substrate. A layer of coating was deposited on the core by arc spraying, and then molten metal was poured into the mould to achieve the combination between substrate and coating. After solidification, the microstructure, chemical compositions and phase constitutions at the interface were analysed. The results show that in the case of casting aluminium or A356 melt around the aluminium coating, metallurgical bonding is formed at the interface after the oxide layer on the surface of coating is broken. There is no continuous metallic transition at the interface of Al coating/Al (Al/Al), while a transition from substrate to coating is formed at the interface of Al coating/A356 (Al/A356). Two diffusion layers are formed at the interface of Al coating/AZ91 (Al/AZ91), and the layers beside the substrate and coating are composed of Al12Mg17+δ (Mg) and Al3Mg2 respectively.

Ferromagnetic films of L10-ordered MnGa and MnAl that exhibit giant perpendicular magnetic anisotropy and great controllability in the magnetism and structural disorders show promise not only in the applications in magnetic recording, permanent magnets and spintronics, but also in controllable studies of disorder-relevant electrical transport phenomena. In this article, we review the intriguing experimental observations of the orbital two-channel Kondo effect and anomalous Hall effect in L10-ordered MnGa and MnAl thin films with perpendicular magnetic anisotropy. We also give a perspective with regards to the future technological and fundamental applications of these perpendicularly magnetized Mn-based binary alloy films., Invited review for spin (submitted)

Oxygen vacancies are widely thought to be responsible for resistive switching (RS) effects based on polycrystalline oxides films. It is also well known that grain boundaries (GB) serve as reservoirs for accumulating oxygen vacancies. Here, Ar gas was introduced to enlarge the size of GB and increase the quantity of oxygen vacancies when the Ba 0.6 Sr 0.4 TiO 3 (BST) films were deposited by pulse laser deposition technique. High resolution transmission electron microscopy images show that an amorphous region GB with large size appears between two lattice planes corresponding to oxygen vacancies defects in the Ar-introduced BST. And we propose that the conduction transport of the cell was dominantly contributed from not ions migration of oxygen vacancies but the electrons in our case according to the value of activation energies of the films.

Bis(tetrabutylammonium)bis(2-thioxo-1,3-dithiole-4,5-dithiolato)mercurate(II) was prepared and characterized by elemental analyses, electronic absorption, infrared and X-ray powder diffraction spectroscopy. The specific heat of the crystal was measured to be 1878.2 J.mol–1K–1 at 300 K. The thermal decomposition process was investigated by means of thermogravimetric analysis and differential thermal analysis measurements in air together with infrared and X-ray powder diffraction spectra. The third-order nonlinear optical properties at 800 nm were measured by femtosecond optical Kerr gate technique by using CS2 as reference. The third-order optical susceptibility of its acetone solution at the concentration of 9.27 × 10–4 M was obtained to be 2.53 × 10–14 esu. The second-order hyperpolarizability was estimated to be 1.7 × 10–32 esu and the response time was about 226 fs. The third order nonlinear optical properties at 532 nm were investigated by using the Z-scan technique with 20 ps. It exhibited self-focusing effect and saturable absorption. The second molecular hyperpolarizability was estimated to be 8.4 × 10–32 esu. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this article the dynamic behavior of clamped-clamped micromachined mechanical resonators working at a frequency of 150kHz was characterized by electrostatic excitation and detection via both capacitive coupling and optical methods. The experimental results by optical measurement show that this system behaved very much like a simple harmonic oscillator at low actuation levels while significant nonlinearity was observed at higher actuation levels. The nonlinearity identified as “spring softening” type occurred when the product of the dc bias voltage and the ac driving voltage exceeded 0.04V2. Dependence of resonance frequency on dc bias voltage was investigated and the experimental results are in agreement with theoretical predictions. This work also demonstrated that optical detection is much less susceptible to parasitic interference than motion detection via capacitive coupling. Therefore, optical techniques will yield better characterization of the mechanical properties of the resonators.

Molecular beam epitaxy of GaSb films, with several percents of Cr, and their characterization are reported. Their electric and magnetic properties depend on their growth temperature and Cr composition. Although magnetization measurements reveal that all the films are ferromagnetic even at room temperature, this is most probably due to the precipitation of ferromagnetic zincblende CrSb. The magnetotransport measurements show that Cr spins may couple antiferromagnetically in GaSb host matrix.

The effects of short fibres on sintering kinetics and shrinkage anisotropy during sintering of composite glass powder compacts are analysed in detail. In sintering composites, short fibres are modelled as prolate spheroidal rigid inclusions randomly dispersed in viscous matrix. Based on the Mori–Tanaka mean-field formulation, the fibre orientation distribution and aspect ratio on viscous matrix sintering have been taken into account. The comprehensively qualitative results for the effects of fibres on whole sintering rate and anisotropy varying with fibre different orientation distributions, aspect ratios and volume fractions are computed. Furthermore, the average internal matrix stress and interfacial normal stresses due to incompatible sintering rates are investigated in this paper.

A summary of detailed measurements of the field- and temperature-dependent ac susceptibility, the field-cooled and zero-field cooled magnetization, coercive field and the resistivity in zero field and applied field of 1.5 T is presented for hole-doped La1−xMgxMnO3 (0.05 ≤ x ≤ 0.4). Measurements of the ac susceptibility enable estimates of the (effective) critical exponents γ, β and δ to be made, which, when combined with the magnetization data, enable a phase diagram to be proposed. The transport data highlight the suppression of a metal–insulator transition in these systems with small average A-site radius. Furthermore, the transport behaviour is shown to be consistent with the predictions for charge transport by conventional small polaron hopping in both the paramagnetic and ferromagnetic phases, but inconsistent with recent quantitative predictions for magnetic small polaron-mediated conduction in a phase-separated picture.

The transport and magnetic behaviours of Ar-annealed (O-depleted) bulk samples of an archetypal, `optimally' doped manganese perovskite, La0.67Ca0.33MnO3, are reported, analysed and compared with those of an untreated specimen. These indicate that the transport data for both the paramagnetic and ferromagnetic phases of the O-depleted system are consistent with the predictions based on polaronic hopping, specifically non-adiabatic small-polaron hopping (on the basis of the internal consistency of estimates for the characteristic frequency Ω0 from both the adiabatic and non-adiabatic formalisms). These results yield indirect support for models which attribute transport in doped perovskites in general, and the colossal-magnetoresistance phenomenon in particular, to polaronic behaviour.

Measurements of the field and temperature dependent electrical resistivity and ac susceptibility of LaMnO3 doped with 5% Mg are presented. Analysis of these data reveal that while this system undergoes a ferromagnetic transition at Tc = 147.2?0.2?K, it remains semiconducting over the entire temperature range examined (90?T?330?K). In particular, these resistivity data are well fit by the form appropriate for adiabatic small polaron hopping for both T>Tc and T

The site preference and magnetic properties of Zn-Zr substituted BaM ferrite BaFe12-xZnx/2Zrx/2O19 nanoparticles with x=0-1.6 have been studied using Mossbauer spectra and magnetic measurement. The results show that the magnetizations and magnetocrystalline anisotropies are closely related to the distributions of Zn-Zr ions on the five sites. The BaFe12-xZnx/2Zrx/2O19 nanoparticles exhibit unusual saturation magnetization, which increase at low substitutions, reach a maximum and then decrease. Massbauer spectra show that the Zn-Zr ions preferentially occupy the 2b and 4f(VI) sites. The preference for the 4f(VI) site is responsible for the anomalous increase in the magnetization at low Zn-Zr substitutions. At x greater than or equal to 1.2 the rapid decrease in the magnetizations is mainly attributed to a noncollinear magnetic structure. In addition, a monotonic decrease in the magnetocrystalline anisotropy with Zn-Zr substitutions has its origin in the preference of the Zn-Zr ions for the 2b and 4f(VI) sites.

Detailed measurements of the field- and temperature-dependent ac susceptibility and magnetization of LaMnO3 substituted with 5 at.% of the divalent cation Mg are presented. This system is a semiconducting ferromagnet at low temperature; in particular, analysis of these data yields Tc = 147.2±0.2 K, with critical exponents δ = 4.75±0.15 (from the field dependence of the susceptibility along the `crossover' line, and confirmed by measurements along the critical isotherm), γ + β = 1.75±0.05 (from the temperature dependence of the crossover line) and γ = 1.39±0.05 (from the temperature dependence of the susceptibility along the same line). Within experimental uncertainty these exponent values agree with those predicted by the isotropic, three-dimensional Heisenberg model. Nevertheless this system exhibits some unusual characteristics, specifically in the temperature dependence of the (low-) field-cooled and zero-field-cooled magnetization. The latter have been modelled by a Preisach-based approach, which helps to resolve a ubiquitous dilemma in the doped manganites, viz. the appearance of a technical hardness irreconcilable with low coercive field values. A possible origin for the large, reversible component in the response below Tc is presented.

We report measurements of the ac susceptibility and dc magnetization of the colossal magnetoresistive pyrochlore ${\mathrm{Tl}}_{2}{\mathrm{Mn}}_{2}{\mathrm{O}}_{7}$ from which we determine the critical temperature ${T}_{c}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}120.65\ifmmode\pm\else\textpm\fi{}0.15\mathrm{K}$ and critical exponents $\ensuremath{\delta}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}4.65\ifmmode\pm\else\textpm\fi{}0.15$ (from the critical isotherm), $\ensuremath{\gamma}+\ensuremath{\beta}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.75\ifmmode\pm\else\textpm\fi{}0.03$ (from the temperature dependence of the crossover line), and $\ensuremath{\gamma}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.31\ifmmode\pm\else\textpm\fi{}0.05$ (from the temperature dependence of the susceptibility along the same line). Unlike recently reported values for perovskite systems, these exponent values are very close to those predicted by the near-neighbor, 3D Heisenberg model. This pyrochlore system, however, exhibits a marked regular (i.e., noncritical) component in the response near ${T}_{c}$, which is unusual in view of the absence of ${\mathrm{Mn}}^{3+}$ ions in this system.

The nanocrystalline structure of annealed Fe73.5Cu1M03Si13.5B9 alloy was investigated using X-ray diffraction and transmission electron microscopy. The relationship between the initial permeability and the microstructural parameters of the annealed alloy is discussed in this paper. The crystalline phase in annealed Fe73.5Cu1M03Si13.5B9 alloy is the α-Fe(Si) phase with a D03 superstructure. The volume fraction, silicon content, and degree of order of the α-Fe(Si) phase increased with an increase in the annealing temperature. In the temperature range of 460–560°C, the α-Fe(Si) phase had a grain size of 14 nm, and its grain number increased as the annealing temperature was increased. The D03 ordered region in the α-Fe(Si) grain was approximately spherical and its size increased as the annealing temperature increased. The size of the D03 ordered region was 14.0 nm at a temperature of 560°C, which is close to that of the α-Fe(Si) grain. There was an obvious change in the microstructure of the residual ...

Tantalum pentoxide (Ta"2O"5) deposited by pulsed DC magnetron sputtering technique as the gate dielectric for 4H-SiC based metal-insulator-semiconductor (MIS) structure has been investigated. A rectifying current-voltage characteristic was observed, with the injection of current occurred when a positive DC bias was applied to the gate electrode with respect to the n type 4H-SiC substrate. This undesirable behavior is attributed to the relatively small band gap of Ta"2O"5 of around 4.3eV, resulting in a small band offset between the 4H-SiC and Ta"2O"5. To overcome this problem, a thin thermal silicon oxide layer was introduced between Ta"2O"5 and 4H-SiC. This has substantially reduced the leakage current through the MIS structure. Further improvement was obtained by annealing the Ta"2O"5 at 900^oC in oxygen. The annealing has also reduced the effective charge in the dielectric film, as deduced from high frequency C-V measurements of the Ta"2O"5/SiO"2/4H-SiC capacitors.

The field- and temperature-dependent ac susceptibility of Mg-substituted LaMnO{sub 3} provides unequivocal evidence for the presence of critical fluctuations associated with a continuous paramagnetic-to-ferromagnetic transition at which all three static critical exponents are estimated independently. Furthermore, this system does not undergo a metal-insulator transition near T{sub c}, exhibiting a monotonic increase in resistivity with decreasing temperature in available fields. Nevertheless, this system displays a near colossal magnetoresistance that peaks near T{sub c}, indicating a probable magnetic origin for this effect but of rather different character from that found in other perovskites. {copyright} {ital 1997} {ital The American Physical Society}

Detailed alternating-current susceptibility and low-field magnetization measurements on samples of Mg-substituted LaMnO3, which x-ray data indicate are orthorhombic, not rhombohedral, show that (i) various oxides of Mn and Mg, which should be present if self-doping occurs, are present at such low levels that they cannot be detected and (ii) the extent of the self-doping of the parent compound La1-yMnO3, if it occurs at all in the sample in question, is at the 1% level. This confirms that Mg does substitute for La in this system.

Measurements of the major hysteresis loop and of the temperature dependence of the field cooled and zero field cooled moment in applied fields less than the coercive field have been performed on two ferromagnetic perovskites La0.95Mg0.05MnO3 and La0.5Sr0.5CoO3. The data have been analyzed within the framework of a generalized Preisach model which includes thermal fluctuations, critical effects, and a temperature dependent distribution of free energy barriers. The analysis shows that the response functions of the manganese perovskite are dominated by the growth of the anisotropy barriers, while in the cobalt perovskite, thermal fluctuations and barrier growth play a roughly equal role.

Detailed measurements of the linear and nonlinear magnetic responses, the zero-field cooled and field-cooled magnetization, and the resistivity of electron-doped ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Mg}}_{x}{\mathrm{MnO}}_{3},$ $0.45l~xl~0.6,$ are summarized. For $0.05l~xl~0.6$ this system exhibits a single paramagnetic to ferromagnetic phase transition on cooling with no thermodynamic reentrant transition to a spin-glass-like phase. Nevertheless, both a detailed analysis of the critical response and the low temperature saturation moment show clear evidence of competing interactions. The latter could arise either as a result of spontaneous electronic phase separation or from conventional noncollinearity (homogeneous, or---due to the random substitution process---inhomogeneous). These results argue against a simple double exchange picture for this system and a uniform ferromagnetic ground state. However, features evident in the zero-field-cooled behavior (and the nonlinear response) at temperatures below ${T}_{c}$ originate from technical sources viz. the increase in coercive field, so it is possible that a gradual onset of competing interactions might arise from a related source. The resistivity data confirm that the complete suppression of a metal-insulator transition in these systems with small average A-site radius extends into the electron-doped regime $(xg~0.5).$ Thus ferromagnetism dominates but the system remains insulating, contrasting with an emerging ferromagnetic metallic state for which a spontaneous electronic phase-separation approach has been proposed. Indeed, the transport data conform with model expressions for charge transport by nonadiabatic small polarons in the paramagnetic phase, but they are quantitatively inconsistent with the expression derived recently by Rahkmanov et al. [Phys. Rev. B $63,$ 174429 (2001)] for the specific model of polaronic hopping in a nonmetallic, phase separated picture.

We present our recent study of non-thermal excitation and coherent control of spin reorientation in 10-nm epitaxially grown Fe thin films by low-energy femtosecond laser pulses. The magnetization dynamics and hysteresis curves were recorded by pump-probe differential magnetic Kerr (DMK) spectroscopy using linearly polarized laser beams. A sharp switching in DMK signal is observed when we rotated the pump polarization. This result indicates a non-thermal origin of magnetization excitation and reorientation in Fe films. We reveal that spins can interact coherently with the polarization induced by the pulsed laser field in magnetic metals. Such opto-magnetic interactions are instantaneous and are only limited in time by the properties of laser pulses. Our results suggest the feasibility of ultrafast optical control of both the magnetization and the demagnetization responses in magnetic films.

Polycrystalline Fe0.4Mn0.6 layers with the different thickness are deposited on 4-nm-thick single-crystalline Co2FeAl layers, which are grown on GaAs (001) substrates at room temperature by molecular-beam epitaxy. Both the exchange bias and the in-plane magnetic anisotropies of the bilayers are strongly dependent on the thickness of the Fe0.4Mn0.6 layer. The former is described using a granular level model. A modified Stoner-Wohlfarth model is used to explain the in-plane magnetic anisotropies observed at 5 K, while one possible reason for the magnetic anisotropies measured at 300 K is the complex interfacial magnetic properties proved by x-ray magnetic circular dichroism measurements.

We fabricated (Ga,Mn)As/AlOx/Co40Fe40B20 magnetic tunnel junctions with ferromagnetic semiconductor/insulator/ferromagnetic metal (S/I/F) structure. The treatments of pre-annealing and post-plasma cleaning on the (Ga,Mn)As film were introduced before the growth of the subsequent layers. A high tunneling magnetoresistance (TMR) ratio of 101% is achieved at 2 K, and the spin polarization of (Ga,Mn)As, P = 56.8%, is deduced from Julliere’s formula. The improved TMR ratio is primarily due to the improved magnetism of (Ga,Mn)As layer by low-temperature annealing and cleaned interface between (Ga,Mn)As and AlOx attained by subsequent plasma cleaning process.

Tunneling magnetoresistance (TMR) in Ga(0.9)2Mn(0.08)As/Al-O/Co40Fe40B20 trilayer hybrid structure as a function of temperature from 10 to 50 K with magnetic field vertical bar H vertical bar

A two-color time-resolved Kerr rotation spectroscopy system was built, with a femtosecond Ti:sapphire laser and a photonic crystal fiber, to study coherent spin transfer processes in an InGaAs/GaAs quantum well sample. The femtosecond Ti:sapphire laser plays two roles: besides providing a pump beam with a tunable wavelength, it also excites the photonic crystal fiber to generate supercontinuum light ranging from 500 nm to 1600 nm, from which a probe beam with a desirable wavelength is selected with a suitable interference filter. With such a system, we studied spin transfer processes between two semiconductors of different gaps in an InGaAs/GaAs quantum well sample. We found that electron spins generated in the GaAs barrier were transferred coherently into the InGaAs quantum well. A model based on rate equations and Bloch-Torrey equations is used to describe the coherent spin transfer processes quantitatively. With this model, we obtain an effective electron spin accumulation time of 21 ps in the InGaAs quantum well.