Effect of Electron-Phonon Scattering on the Anomalous Hall Conductivity of Fe3_3Sn: A Kagome Ferromagnetic Metal

We report on magnetic and magnetotransport studies of a Kagome ferromagnetic metal, Fe$_3$Sn. Our studies reveal a large anomalous Hall conductivity ($\sigma_{zx}$) in this system, mainly contributed by temperature independent intrinsic Hall conductivity ($\sigma^{int}_{zx}$=485$\pm$60 S/cm) and temperature dependent extrinsic Hall conductivity ($\sigma^{ext}_{zx}$) due to skew-scattering. Although $\sigma^{ext}_{zx}$ value is large and almost equivalent to the intrinsic Hall conductivity at low temperatures, it drastically decreases with increasing temperature, following the relation $\sigma^{ext}_{zx}=\frac{\sigma_{zx0}^{ext}}{(aT+1)^2}$, under the influence of electron-phonon scattering. The presence of electron-phonon scattering in this system is also confirmed by the linear dependence of longitudinal electrical resistivity at higher temperatures [$\rho(T)\propto T$]. We further find that Fe$_3$Sn is a soft ferromagnet with an easy-axis of magnetization lying in the $\it{ab}$ plane of the crystal with magnetocrystalline anisotropy energy density as large as 1.02 $\times$ 10$^6$Comment: 8 pages and 4 figures, accepted in Phys. Rev.

Large Room-Temperature Pure Topological Hall Effect (THE) in Kagome Antiferromagnet Mn3_3Sn, and Induced Giant Low-Temperature THE with Fe Doping

Mn$_3$Sn is a fascinating magnetic topological system, showing topological characteristics within the Kagome lattice network due to the non-vanishing Berry phase in the momentum space. In this study, for the first time, we show a large pure room-temperature topological Hall effect (THE) in the $xy$-plane (0001), while the anomalous Hall effect (AHE) has been noticed in the $zx$-plane (01$\bar{1}$0) of Mn$_3$Sn. With Fe doping, we can induce a giant $xy$-plane THE in addition to AHE at low temperatures, while still preserving the pure room-temperature THE in Mn$_{2.8}$Fe$_{0.2}$Sn. Moreover, the AHE in the $zx$-plane has been increased with Fe doping. Our studies indicate that the topological properties are highly anisotropic in these systems. Most importantly, the large room-temperature pure THE observed in Mn$_3$Sn is quite promising for the realization of room-temperature topotronic-based applicationsComment: 10 pages and 6 figure

Investigation of the Anomalous and Topological Hall Effects in Layered Monoclinic Ferromagnet Cr2.76_{2.76}Te4_4

We studied the electrical transport, Hall effect, and magnetic properties of monoclinic layered ferromagnet Cr$_{2.76}$Te$_4$. Our studies demonstrate Cr$_{2.76}$Te$_4$ to be a soft ferromagnet with strong magnetocrystalline anisotropy. Below 50 K, the system shows an antiferromagnetic-like transition. Interestingly, between 50 and 150 K, we observe fluctuating magnetic moments between in-plane and out-of-plane orientations, leading to non-coplanar spin structure. On the other hand, the electrical resistivity data suggest it to be metallic throughout the measured temperature range, except a $kink$ at around 50 K due to AFM ordering. The Rhodes-Wohlfarth ratio $\frac{\mu_{eff}}{\mu_{s}}=1.89 (>1)$ calculated from our magnetic studies confirms that Cr$_{2.76}$Te$_4$ is an itinerant ferromagnet. Large anomalous Hall effect has been observed due to the skew-scattering of impurities and the topological Hall effect has been observed due to non-coplanar spin-structure in the presence of strong magnetocrystalline anisotropy. We examined the mechanism of anomalous Hall effect by employing the first principles calculations.Comment: 9 pages, 6 figures, To appear in Physical Review Material

Tuning of Electrical, Magnetic, and Topological Properties of Magnetic Weyl Semimetal Mn3+x_{3+x}Ge by Fe doping

We report on the tuning of electrical, magnetic, and topological properties of the magnetic Weyl semimetal (Mn$_{3+x}$Ge) by Fe doping at the Mn site, Mn$_{(3+x)-\delta}$Fe$_{\delta}$Ge ($\delta$=0, 0.30, and 0.62). Fe doping significantly changes the electrical and magnetic properties of Mn$_{3+x}$Ge. The resistivity of the parent compound displays metallic behavior, the system with $\delta$=0.30 of Fe doping exhibits semiconducting or bad-metallic behavior, and the system with $\delta$=0.62 of Fe doping demonstrates a metal-insulator transition at around 100 K. Further, we observe that the Fe doping increases in-plane ferromagnetism, magnetocrystalline anisotropy, and induces a spin-glass state at low temperatures. Surprisingly, topological Hall state has been noticed at a Fe doping of $\delta$=0.30 that is not found in the parent compound or with $\delta$=0.62 of Fe doping. In addition, spontaneous anomalous Hall effect observed in the parent system is significantly reduced with increasing Fe doping concentration.Comment: 16 pages and 5 figures, accepted in Journal of Physics: Condensed Matte

Weak Electronic Correlations Observed in Magnetic Weyl Semimetal Mn3_3Ge

Using angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT) calculations, we systematically studied the electronic band structure of Mn$_3$Ge in the vicinity of the Fermi level. We observe several bands crossing the Fermi level, confirming the metallic nature of the studied system. We further observe several flat bands along various high symmetry directions, consistent with the DFT calculations. The calculated partial density of states (PDOS) suggests a dominant Mn $3d$ orbital contribution to the total valence band DOS. With the help of orbital-resolved band structure calculations, we qualitatively identify the orbital information of the experimentally obtained band dispersions. Out-of-plane electronic band dispersions are explored by measuring the ARPES data at various photon energies. Importantly, our study suggests relatively weaker electronic correlations in Mn$_3$Ge compared to Mn$_3$Sn.Comment: 11 pages, 3 figures. To appear in the Journal of Physics: Condensed Matte