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- ItemTopological Hall effect in thin films of Mn1.5PtSn(College Park, MD : APS, 2019) Swekis, Peter; Markou, Anastasios; Kriegner, Dominik; Gayles, Jacob; Schlitz, Richard; Schnelle, Walter; Goennenwein, Sebastian T.B.; Felser, ClaudiaSpin chirality in metallic materials with noncoplanar magnetic order can give rise to a Berry phase induced topological Hall effect. Here, we report the observation of a large topological Hall effect in high-quality films of Mn1.5PtSn that were grown by means of magnetron sputtering on MgO(001). The topological Hall resistivity is present up to μ0H≈4T below the spin reorientation transition temperature, Ts=185 K. We find that the maximum topological Hall resistivity is of comparable magnitude as the anomalous Hall resistivity. Owing to the size, the topological Hall effect is directly evident prior to the customarily performed subtraction of magnetometry data. Further, we underline the robustness of the topological Hall effect in Mn2-xPtSn by extracting the effect for multiple stoichiometries (x=0.5,0.25,0.1) and film thicknesses (t=104,52,35 nm) with maximum topological Hall resistivities between 0.76 and 1.55μΩcm at 150 K. © 2019 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
- ItemA New Highly Anisotropic Rh-Based Heusler Compound for Magnetic Recording(Weinheim : Wiley-VCH, 2020) He, Yangkun; Fecher, Gerhard H.; Fu, Chenguang; Pan, Yu; Manna, Kaustuv; Kroder, Johannes; Jha, Ajay; Wang, Xiao; Hu, Zhiwei; Agrestini, Stefano; Herrero-Martín, Javier; Valvidares, Manuel; Skourski, Yurii; Schnelle, Walter; Stamenov, Plamen; Borrmann, Horst; Tjeng, Liu Hao; Schaefer, Rudolf; Parkin, Stuart S.P.; Coey, John Michael D.; Felser, ClaudiaThe development of high-density magnetic recording media is limited by superparamagnetism in very small ferromagnetic crystals. Hard magnetic materials with strong perpendicular anisotropy offer stability and high recording density. To overcome the difficulty of writing media with a large coercivity, heat-assisted magnetic recording was developed, rapidly heating the media to the Curie temperature Tc before writing, followed by rapid cooling. Requirements are a suitable Tc, coupled with anisotropic thermal conductivity and hard magnetic properties. Here, Rh2CoSb is introduced as a new hard magnet with potential for thin-film magnetic recording. A magnetocrystalline anisotropy of 3.6 MJ m−3 is combined with a saturation magnetization of μ0Ms = 0.52 T at 2 K (2.2 MJ m−3 and 0.44 T at room temperature). The magnetic hardness parameter of 3.7 at room temperature is the highest observed for any rare-earth-free hard magnet. The anisotropy is related to an unquenched orbital moment of 0.42 μB on Co, which is hybridized with neighboring Rh atoms with a large spin–orbit interaction. Moreover, the pronounced temperature dependence of the anisotropy that follows from its Tc of 450 K, together with a thermal conductivity of 20 W m−1 K−1, make Rh2CoSb a candidate for the development of heat-assisted writing with a recording density in excess of 10 Tb in.−2. © 2020 The Authors. Published by Wiley-VCH GmbH
- ItemThermoelectric Properties of Novel Semimetals: A Case Study of YbMnSb2(Weinheim : Wiley-VCH, 2020) Pan, Yu; Fan, Feng-Ren; Hong, Xiaochen; He, Bin; Le, Congcong; Schnelle, Walter; He, Yangkun; Imasato, Kazuki; Borrmann, Horst; Hess, Christian; Büchner, Bernd; Sun, Yan; Fu, Chenguang; Snyder, G. Jeffrey; Felser, ClaudiaThe emerging class of topological materials provides a platform to engineer exotic electronic structures for a variety of applications. As complex band structures and Fermi surfaces can directly benefit thermoelectric performance it is important to identify the role of featured topological bands in thermoelectrics particularly when there are coexisting classic regular bands. In this work, the contribution of Dirac bands to thermoelectric performance and their ability to concurrently achieve large thermopower and low resistivity in novel semimetals is investigated. By examining the YbMnSb2 nodal line semimetal as an example, the Dirac bands appear to provide a low resistivity along the direction in which they are highly dispersive. Moreover, because of the regular-band-provided density of states, a large Seebeck coefficient over 160 µV K−1 at 300 K is achieved in both directions, which is very high for a semimetal with high carrier concentration. The combined highly dispersive Dirac and regular bands lead to ten times increase in power factor, reaching a value of 2.1 mW m−1 K−2 at 300 K. The present work highlights the potential of such novel semimetals for unusual electronic transport properties and guides strategies towards high thermoelectric performance. © 2020 The Authors. Advanced Materials published by Wiley-VCH GmbH