Browsing by Subject "Resistivity measurements"

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    Helical magnetic order and Fermi surface nesting in non-centrosymmetric ScFeGe
    (American Physical Society, 2021) Karna, Sunil K.; Tristant, D.; Hebert, J. K.; Cao, G.; Chapai, R.; Phelan, W. A.; Zhang, Q.; Wu, Y.; Dhital, C.; Li, Y.; Cao, H. B.; Tian, W.; Dela Cruz, C. R.; Aczel, A. A.; Zaharko, O.; Khasanov, A.; McGuire, M. A.; Roy, A.; Xie, W.; Browne, D. A.; Vekhter, I.; Meunier, V.; Shelton, W. A.; Adams, P. W.; Sprunger, P. T.; Young, D. P.; Jin, R.; DiTusa, J. F.; Physics, School of Science
    An investigation of the structural, magnetic, thermodynamic, and charge transport properties of noncentrosymmetric hexagonal ScFeGe reveals it to be an anisotropic metal with a transition to a weak itinerant incommensurate helimagnetic state below 𝑇𝑁=36 K. Neutron diffraction measurements discovered a temperature and field independent helical wave vector 𝒌 = (0 0 0.193) with magnetic moments of 0.53 𝜇𝐵 per Fe confined to the 𝑎⁢𝑏 plane. Density functional theory calculations are consistent with these measurements and find several bands that cross the Fermi level along the 𝑐 axis with a nearly degenerate set of flat bands just above the Fermi energy. The anisotropy found in the electrical transport is reflected in the calculated Fermi surface, which consists of several warped flat sheets along the 𝑐 axis with two regions of significant nesting, one of which has a wave vector that closely matches that found in the neutron diffraction. The electronic structure calculations, along with a strong anomaly in the 𝑐 -axis conductivity at 𝑇𝑁, signal a Fermi surface driven magnetic transition, similar to that found in spin density wave materials. Magnetic fields applied in the 𝑎⁢𝑏 plane result in a metamagnetic transition with a threshold field of ≈6.7 T along with a sharp, strongly temperature dependent discontinuity and a change in sign of the magnetoresistance for in-plane currents. Thus, ScFeGe is an ideal system to investigate the effect of in-plane magnetic fields on a helimagnet with a 𝑐 -axis propagation vector, where the relative strength of the magnetic interactions and anisotropies determine the topology and magnetic structure.
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    Large Exotic Spin Torques in Antiferromagnetic Iron Rhodium
    (APS, 2022-08) Gibbons, Jonathan; Dohi, Takaaki; Amin, Vivek P.; Xue, Fei; Ren, Haowen; Xu, Jun-Wen; Arava, Hanu; Shim, Soho; Saglam, Hilal; Liu, Yuzi; Pearson, John E.; Mason, Nadya; Petford-Long, Amanda K.; Haney, Paul M.; Stiles, Mark D.; Fullerton, Eric E.; Kent, Andrew D.; Fukami, Shunsuke; Hoffman, Axel; Physics, School of Science
    Spin torque is a promising tool for driving magnetization dynamics for computing technologies. These torques can be easily produced by spin-orbit effects, but for most conventional spin source materials, a high degree of crystal symmetry limits the geometry of the spin torques produced. Magnetic ordering is one way to reduce the symmetry of a material and allow exotic torques, and antiferromagnets are particularly promising because they are robust against external fields. We present spin torque ferromagnetic resonance (ST-FMR) measurements and second harmonic Hall measurements characterizing the spin torques in antiferromagnetic iron rhodium alloy. We report extremely large, strongly temperature-dependent exotic spin torques with a geometry apparently defined by the magnetic ordering direction. We find the spin torque efficiency of iron rhodium to be (207 ± 94)% at 170 K and (88 ± 32)% at room temperature. We support our conclusions with theoretical calculations showing how the antiferromagnetic ordering in iron rhodium gives rise to such exotic torques.