iron and ferroalloys, and magnetic properties of anomalous Hall effect

　　Title: iron and ferroalloys, and magnetic properties of anomalous Hall effect
　　Author: Tian Yuan
　　Degree-granting units: Fudan University
　　Keywords: anomalous Hall effect;; Berry phase;; skew scattering;; side jump;; localization;; molecular beam epitaxy;; membrane transport;; magneto-optical Kerr effect
　　Abstract:
　　Magnetic study of people over the past two decades, there had been a new development. Magnetic properties no longer limited to the macro, the static magnetic material, but extended to the study of single electron, the spin state changes in transport. The main driving force Neodymium Magnet in this area comes from people hoping to use the electron spin degree of freedom to carry information and calculations. Experiment, people found a tunnel magnetoresistive (TMR) and Pang magnetoresistance (CMR), the spin Hall effect, spin torque, anomalous Hall effect, spin quantum Hall effect and so a series of new phenomena, and thus develop into a device structure that contains a variety of design, research and a variety of mechanisms of the huge variety of materials preparation area - spintronics.
　　In spintronics lineup, anomalous Hall effect (anomalous Hall effect, AHE) is undoubtedly a wonderful work. Because of this phenomenon in 1889, I found that Hall had been. But on the mechanism comes from the non-intrinsic mechanisms or intrinsic mechanisms of controversy continues to this day. Several existing mechanisms, including 1954 Kaplus and Luttinger's band structure and spin-orbit coupling determines the intrinsic mechanism, proposed in 1955 by Smit scattering and spin-orbit coupling caused by oblique scattering mechanisms (skew scattering) and 1971 Berger's side jump in non-intrinsic mechanism. The complex theoretical models and experimental results make a simple experiment can not end this debate. Today, it was discovered that AHE mechanism also applies to the spin Hall effect. This makes its mechanism from the intrinsic or extrinsic, the scale changes with temperature and how the discussion is particularly important. In this article, the author of the classic system of AHE-Fe single crystal studied. In the GaAs (001) and MgO (001) two kinds of substrates of Fe single crystal epitaxial growth, the use of change measures to regulate the thickness of the non-intrinsic scattering size. Worthy of note is that this method to change the non-intrinsic scattering within a certain range, while maintaining the intrinsic mechanism remains unchanged. This overcomes the traditional change through non-doped intrinsic http://www.everbeenmagnet.com/ scattering approach in changing the extrinsic scattering intensity also changes the intrinsic mechanism of the defects. It is this characteristic allows us to obtain many new results, including:
　　1 proved long been considered anomalous Hall resistivity and extrinsic scattering
　　Strength (longitudinal resistivity) can not describe the relationship between the function of iron in the finite temperature experimental data. Then the experimental data established a new function. New function to unify the description of the past relationship in different systems, different temperatures of the complex experimental results, the function respectively skewscattering, side jump, and intrinsic mechanisms linked. More importantly, it is not clear enough before the limited theoretical understanding of experimental results the temperature of a summary, which will promote the further improvement of the theory.
　　2 different designs through the samples, showing the interface of the regulation, and changes in substrate doping on the intrinsic differences and non-intrinsic mechanisms of the effects. Established prior to the function that the relationship for Fe-based alloys. Anomalous Hall conductivity for low temperatures, a slight deviation from the functional relation of the phenomena studied discussion. This deviation may indicate that the Fe-magnetic metal alloy contains not considered anomalous Hall effect.
　　3 Based on the progress of the previous study of the anomalous Hall effect in low-dimensional changes observed with the thickness of the intrinsic effects of reduced and reduced, non-intrinsic effects of the phenomenon is almost unchanged. Of the possible causes were discussed. This part of the experimental results for the first-principles calculations provide a reference object. In addition, also observed in thin ferromagnetic material when the localization phenomenon. With previous research, to determine the Fe film on GaAs substrate non-intrinsic scattering mechanisms included in a strong side jump mechanism, which supports the function of thick-film drawn in a side jump mechanism is the inference. Fe film on MgO substrate side jump rarely.
　　The last part of this paper is the author of the film magneto-optical Kerr effect of numerical calculation. Compared with the experimental results, indicating that the nano-scale magneto-optical Kerr effect of Fe is greater than the material constants may be under the circumstances. The Fe and Au and other optical constants are changed little. The results also show that a slight deviation from the optical constants for the isotropic case, such as some of the MBE epitaxial growth of materials, magneto-optical Kerr effect can be used to determine the size of the anisotropy constant.