Hall effect in Al-W thin films

The Hall coefficient, R_H, electrical resistivity, ρ, and temperature coefficient of resistivity, α, of Al_xW_100−x (61≤x≤88) thin films and amorphous-like tungsten films are reported. The Al_xW_100−x films have been prepared by magnetron co-deposition of pure metals onto glass substrate. Films are X-ray amorphous for 63≤x≤86. Amorphous-like tungsten films (x=0) were obtained at sputtering conditions different from those applied for the preparation of Al-W alloys. The R_H value is strongly dependent upon the alloy composition: it changes sign from positive to negative at x≈78, and exhibits a maximum for x≈68 at.%. With the decrease of Al content, ρ steeply increases and exhibits a maximum at x≈80 at.%. The temperature coefficient of the resistivity exhibits large negative values, with a well-defined minimum at x≈80. The Hall coefficient of films with 67≤x≤80 has also been determined at liquid nitrogen temperature, and the values obtained were the same as the room temperature values. Since the value of electrical resistivity of the examined alloys in the temperature interval from 77 to 300 K noticeably changes (10%), a significant anomalous contribution to the Hall effect is thus excluded.     

Hall effect in thin films of nickel-phosphorus

The Hall effect in nickel-phosphorus thin films prepared by oxydo-reduction in liquid phase, is greatly influenced by the phosphorus present in the deposit by an important effect in structure. The conductivity is electronic. The results are in agreement with the present theories of the Hall effect in ferromagnets.     

Anomalous Hall effect in polycrystalline Ni films

We systematically studied the anomalous Hall effect in a series of polycrystalline Ni films with thickness ranging from 4 to 200 nm. It is found that both the longitudinal and anomalous Hall resistivity increased greatly as film thickness decreased. This enhancement should be related to the surface scattering. In the ultrathin films (4–6 nm thick), weak localization corrections to anomalous Hall conductivity were studied. The granular model, taking into account the dominated intergranular tunneling, has been employed to explain this phenomenon, which can explain the weak dependence of anomalous Hall resistivity on longitudinal resistivity as well.     

Anomalous Hall effect in highly Mn-Doped silicon films

The transport and magnetic properties of Mn _x Si_{1 ? x} films with a high (x ≈ 0.35) content of Mn produced by laser deposition at growth temperatures of 300–350°C have been studied in a temperature range of 5–300 K in magnetic fields of up to 2.5 T. The films exhibit a hole-type metallic conductivity and a relatively weak change of magnetization in a temperature range of 50–200 K. An anomalous Hall effect with an essentially hysteretic behavior from 50 K up to ≈230 K has been discovered. The properties of the films are explained by the two-phase model, in which ferromagnetic clusters containing interstitial Mn ions with a localized magnetic moment are embedded in the matrix of a weak band MnSi_{2 ? x} (x ≈ 0.3) type ferromagnet with delocalized spin density.     

Anomalous Hall effect in perpendicular CoFeB thin films

Our recent research achievements in the perpendicular magnetic anisotropy （PMA） properties of the CoFeB sand- wiched by MgO and tantalum layers are summarized. We found that the PMA behaviors of Ta/CoFeB/MgO and MgO/CoFeB/Ta thin films are different. The larger PMA in the latter film is related to the lower magnetization of CoFeB deposited on MgO. Furthermore, we have demonstrated a large anomalous Hall effect in perpendicular CoFeB thin fihn. Our results show large anomalous Hall resistivity, large longitudinal resistivity, and low switching field can be achieved, all at the same time, in the perpendicular CoFeB thin film. Anomalous Hall effect with high and linear sensitivity is also found in an MgO/CoFeBFFa thin film with a thick MgO layer, which opens a door tbr future device applications of perpendicular ferromagnetic thin films.     

金属薄膜中的逆自旋霍尔效应

自旋流的产生和测量是自旋电子学面临的重大挑战.逆自旋霍尔效应提供了对自旋流进行电学测量的有效手段.文章总结了近年来人们对金属薄膜中的逆自旋霍尔效应的研究,从非局域电注入、铁磁共振注入、声波共振注入和圆偏振光注入这四种不同的自旋流注入方式来介绍逆自旋霍尔效应的物理机制、实现方式和影响因素.     

金属薄膜中的逆自旋霍尔效应

自旋流的产生和测量是自旋电子学面临的重大挑战．逆自旋霍尔效应提供了对自旋流进行电学测量的有效手段．文章总结了近年来人们对金属薄膜中的逆自旋霍尔效应的研究,从非局域电注入、铁磁共振注入、声波共振注入和圆偏振光注入这四种不同的自旋流注入方式来介绍逆自旋霍尔效应的物理机制、实现方式和影响因素．     

Electromigration and transport reversal in copper-silver thin films

Grain boundary electrotransport of copper and silver atoms in copper + 1·2 at.% silver thin film conductors has been found to take place in opposite directions; the copper atoms migrate against the direction of electron flow, while the silver atoms migrate along this direction. It is shown that both the transport directions of the copper and the silver atoms can be qualitatively interpreted in terms of the existing theories of electromigration.     

The Hall effect of thin iron films

A curvature invariant of spacetimes that are solutions to the Einstein-Cartan-Weyl equations is studied. It is found that in the static plane symmetric case this invariant is singular.     

Anomalous Hall effect and electron transport in ferromagnetic MnBi films

The electron transport properties of highly c-axis oriented MnBi thin films of various thicknesses have been investigated. Samples are metallic but the low temperature resistivity shows an unusual T(3) dependence. Transverse Hall effect measurements show that both the ordinary and anomalous Hall coefficients decrease with decreasing temperature below 300 K, but the ordinary Hall coefficient (R(0)) undergoes a sign reversal around 105 K, where the magnetic anisotropy also changes sign. Analysis of the Hall data for various samples shows that the anomalous Hall coefficient (R(s)) exhibits a strong ρ(2) dependence, where ρ is the longitudinal resistivity.     

The spin Hall effect in single-crystalline gold thin films

The spin Hall effect has been investigated in 10-nm-thick epitaxial Au(001) single crystal films via H-pattern devices,whose minimum characteristic dimension is about 40 nm. By improving the film quality and optimizing the in-plane geometry parameters of the devices, we explicitly extract the spin Hall effect contribution from the ballistic and bypass contribution which were previously reported to be dominating the non-local voltage. Furthermore, we calculate a lower limit of the spin Hall angle of 0.08 at room temperature. Our results indicate that the giant spin Hall effect in Au thin films is dominated not by the interior defects scattering, but by the surface scattering. Besides, our results also provide an additional experimental method to determine the magnitude of spin Hall angle unambiguously.     

Giant Hall effect in nonmagnetic granular metal films.

Nearly 3 orders of magnitude enhancement in the Hall coefficient is observed in Cu(x)-(SiO(2))(1--x) granular films. This large enhancement of the Hall coefficient not only is significantly larger than the prediction of the classical percolation theory, but also occurs at a metal concentration identified to be the quantum percolation threshold. Measurements of the electron dephasing length and magnetoresistance, plus the TEM characterization of microstructures, yield a physical picture consistent with the mechanism of the local quantum interference effect.     

Hall effect of tetragonal and orthorhombic SrRuO3 films

High quality orthorhombic and tetragonal SrRuO₃ thin films were grown by pulsed laser deposition on SrTiO₃(001) and Ba_0.75Sr_0.25TiO₃ buffered LaAlO₃(001) substrates. Resistivity vs. temperature curves showed a slope change at a Curie temperature of 147.5 ± 2 K for 40 nm thick films irrespective of crystalline symmetry. The Hall resistivity of both films contained an anomalous Hall contribution. The anomalous Hall coefficient was positive throughout the whole temperature range for the tetragonal film, whereas it showed a sign change at 143 K for the orthorhombic film. This is a strong indication that the Berry‐phase mechanism is the dominant anomalous Hall effect mechanism in SrRuO₃. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

不同织构CVD金刚石膜的Hall效应特性

采用热丝化学气相沉积法在p型硅衬底上制备了不同织构的多晶金刚石膜,使用XRD表征了CVD金刚石膜的结构特征, 研究了退火后不同织构金刚石膜的电流特性, 使用Hall效应检测仪研究了金刚石膜的霍尔效应特性及随温度变化的规律, 结果表明所制备的金刚石膜是p型材料, 载流子浓度随着温度的降低而增加, 迁移率随着温度的降低而减小. 室温下[100]织构金刚石薄膜的载流子浓度和迁移率分别为4.3×10⁴ cm^-3和76.5 cm²/V·s.     

Temperature effect on structural transformations in nanocrystalline cobalt films

The effect of annealing temperature on the structure and magnetic properties of nanocrystalline cobalt films has been studied by nuclear magnetic resonance (NMR) and magnetometric (vibrational magnetometer) techniques. Interpretation of the experimental data demonstrates that the initial films have an amorphous-like structure due to the high degree of disordering in the intergranular regions and nanoparticles. This structure transforms into the equilibrium polycrystalline state through the formation of a number of intermediate phases.