Magnetic Weyl semimetals with spontaneously broken time-reversal symmetry exhibit a large intrinsic anomalous Hall effect originating from the Berry curvature. To employ this large Hall current for room temperature topo-spintronics applications, it is necessary to fabricate these materials as thin or ultrathin films. Here, we experimentally demonstrate that Weyl semimetal Co2MnGa thin films (20–50 nm) show a large anomalous Hall angle ~11.4% at low temperature and ~9.7% at room temperature, which can be ascribed to the non-trivial topology of the band structure with large intrinsic Berry curvature. However, the anomalous Hall angle decreases significantly with thicknesses below 20 nm, which band structure calculations confirm is due to the reduction of the majority spin contribution to the Berry curvature. Our results suggest that Co2MnGa is an excellent material to realize room temperature topo-spintronics applications; however, the significant thickness dependence of the Berry curvature has important implications for thin-film device design.
Anomalous Hall and anomalous Nernst properties of thin MgO/Co2Fe0.4Mn0.6Si/Pd stacks with perpendicular magnetic anisotropy (PMA) revealed the presence of the magnetic proximity effect (MPE) in the Pd layer. The MPE is evidenced by nanometer range thickness-dependent transport measurements. A three-layer model that combines bulk and interface contributions accounts for our experimental data and provides quantitative estimates for the contributions to the total anomalous Nernst voltage of the ferromagnet Heusler [+0.97 μV/(K nm)] and the proximity-magnetized Pd layers [−0.17 μV/(K nm)]. The anomalous Nernst effect (ANE) reverses its sign by tuning the thickness of the Heusler layer, which is useful for designing ANE thermopiles.
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