Digital applications of the planar Hall effect in ferromagnetic thin films

The planar Hall effect in ferromagnetic thin films has been optimized with respect to composition dependence and geometric structure. Various devices can be realized with this effect, using the output voltage or the output current in a short circuited loop.This work was sponsored by Délégation Générate á la Recherche Scientifique et Technique.The authors thank R. Morille for the preparation of thin films.     

Quantum size effects for the extraordinary Hall effect in thin magnetic films

A theory for the extraordinary Hall effect in thin films is derived using the Kubo formalism. We calculate the skew-scattering contribution to the Hall resistivity. Oscillations of the resistivity with the thickness of the magnetic layers are obtained similar to the diagonal resistivity, but as the Hall current is due to d-electrons, the period of these oscillations is connected with the Fermi wave vector of the d-electrons.     

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.     

Thickness dependence of the magnetic properties and magnetoimpedance effect in CoFeAlO thin films

The change of the magnetic properties and magnetoimpedance effect of Co–Fe–Al–O thin films with film thicknesses 50–1200 nm has been investigated. The coercivity and the anisotropy field changed strongly with increase of film thickness, while the saturation induction almost remained unchanged. The maximum value of GMI effect obtained about 33% for a film thickness of 1200 nm.     

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.     

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.     

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．     

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.     

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.     

Anisotropic magnetocaloric effect in thin magnetic films

We consider the magnetocaloric effect in thin magnetic films. The experimental method is based on heat transfer in a layered structure containing a magnetic film and a film of material with a metal-dielectric phase transition. The anisotropy of the magnetocaloric effect is studied.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 40–43, November, 1989.The authors thank G. A. Petrakovskii and V. G. Pyn'ko for useful discussions.     

Unusual field dependence of the Hall effect in Ni3Mn films

An anomalous behavior of the Hall emf E_h in disordered Ni₃Mn vacuum condensates is discovered. As the magnetic field H is increased from zero, E_h first increases in absolute value, its sign being negative. At a certain field, E_h then begins to decrease, passes through zero, and subsequently approaches saturation in the normal manner, its sign being positive. This behavior can be explained by assuming the presence in the condensate of several magnetic phases with emf values of different signs and with different saturation fields.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 101–104, December, 1976.     

Hall effect and pinning regimes in thin films doped with nanoparticles

Hall effect and flux pinning in YBa₂Cu₃O_6+x (YBCO) thin films doped with BaZrO₃ (BZO) nanoparticles is investigated. The results show that sign reversal of the Hall coefficient from positive hole-like to negative electron-like occurs in vortex-liquid regime of undoped and BZO-doped YBCO films. With increasing BZO concentration the amplitude of the negative Hall effect is suppressed while the temperature position of the anomalous Hall effect does not depend significantly on doping level. In addition, it is shown that Hall conductivity increases non-monotonically with increasing BZO doping. These results support a model where BZO at low doping concentration induces point pinning centres turning to strong columnar pinning defects in films doped with 4% BZO.