| The development of Spintronics dictates a better understanding towards the spin-dependent transport phenomena. Attention has been attracted to long s-tanding issues such as anomalous Hall effect (AHE), the mechanisms of which turn out governing other transport effect related to spin-orbit physics, e.g. the spin Hall effect. There are three mechanisms proposed to explain AHE, includ-ing the extrinsic mechanisms skew scattering and side jump, and the intrinsic mechanism which is related to the k-space Berry phase gained by the conduction electrons under the presence of spin-orbital coupling. However, finding the ex-perimental correspondence to these mechanisms has been an unsolved issue for more than half a century. For example, the side jump and intrinsic mechanisms, because of their similar scaling relation with longitudinal resistivity, can hardly be distinguished experimentally.The topological spin structure, on the other hand, is another source of A-HE beyond the existing three mechanisms. The additional Berry phase gained by the conduction electrons hoping over sites with slowly varying local magnetic moment in real space will give rise to AHE, or sometimes called topological Hall effect (THE), in a similar way as the intrinsic mechanism. These topologically non-trivial magnetic structures are attracting a great deal of interest because of the rich underlying physics and potential applications. One of the most intriguing examples called skyrmion, in which the constituent spins point in all directions wrapping up a sphere, has recently been observed in B20-type chiral magnets. It is found that the skyrmion magnetic structure poses unusual response to electric charge current and spin current and can be driven by an ultra-low current den-sity. The intriguing physical properties accompanied by high controllability are intriguing for its future applications as spintronic devices. Studying the THE will not only help understanding the Berry phase related physics, but also provides the read-out technique if the nano-meter-scale magnetic structures will one day be used as high density storage device.This essay will therefore be dedicated to the following three topics:1. The AHE in epitaxial Ni34Cu66thin film is investigated, in which different mechanisms is distinguished by the dependence on longitudinal resistivity. The absence of ferromagnetism excludes the intrinsic mechanism, and thus ascribes the quadratic term to side jump and the linear term to skew scat-tering. The presence of the side jump mechanism is verified unambiguously and further analysis suggests that only elastic scattering process contributes to the side jump mechanism.2. Towards the’skyrmionics’. not bulk but thin-film specimens will be appreci-ated, not only because the top-down device fabrication procedure is capable, but also because the skyrmion phase in thin films is expected to be stabi-lized in a much wider temperature-magnetic field (T-H) region, compared with the bulk specimen. However, skyrmions in epitaxial thin film has never been evidenced unambiguously. We report here the first realization of high-quality epitaxial MnSi/Si(111) thin film that hosts skyrmion spin texture. The clear-cut real-space observations of skyrmion spin texture are achieved using a high-resolution Lorentz transmission electron microscopy (TEM).3. With a detailed analysis of the AHE of MnSi thin films which finds skew scattering and the intrinsic terms, we have unambiguously separated the THE and established the link between THE and skyrmion formation, which conclude the robust skyrmion phase over a wide T-H plane. In addition, we also found distinctive features in THE which are beyond the current understanding of skyrmion-related physics. The discrepancy would advance the theories on skyrmions to the next stages.
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