Helical magnetic order and Fermi surface nesting in noncentrosymmetric ScFeGe

Abstract

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 T N = 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 μ B per Fe confined to the ab 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 T N , signal a Fermi surface driven magnetic transition, similar to that found in spin density wave materials. Magnetic fields applied in the ab 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.

First principle study of scandium-based novel ternary half Heusler ScXGe (X = Mn and Fe) alloys: insight into the spin-polarized structural, electronic, and magnetic properties

“…Following the acquisition of the magnetic stable state, we proceeded to assess the thermodynamic stabilities through the calculation of the formation energy, denoted as E f 33–36 where E tot is the calculated total energy per unit cell, μ i is atomic chemical potential for element i, and the x i is the quantity of element i. Formation energy is the energy needed to break the bonds separating atoms in a solid state.…”

“…The calculated properties align generally with previous DFT results but slightly underestimate experimental data, likely due to the absence of lattice dynamics at T = 0 K, whereas experiments were conducted at room temperature. Sunil K. Karna et al 19 thoroughly examined the temperature-dependent properties of the noncentrosymmetric hexagonal ScFeGe system, including its structure, magnetism, thermodynamics, and charge transport. They prepared polycrystalline samples via arc melting and analyzed them using various techniques such as PXRD, EPMA, MPMS SQUID magnetometer, NPD, and XANES spectroscopy.…”

“…Previous research by Karna et al 19 shown that structural, magnetic, thermodynamic, and charge transport parameters reveal anisotropic metallic behavior in non-centrosymmetric hexagonal ScFeGe, which is characterized by a weak itinerant incommensurate helimagnetic state below T N = 36 K. A temperature and field-independent helical wave vector k = (0 0 0.193) with magnetic moments of 0.53 bohr magnetons per formula unit were found in the neutron diffraction experiments, which is primarily confined to the ab -plane. We have examined the structural, electrical, and magnetic characteristics of ScXGe (where X = Mn, Fe) in this study.…”

Discovery of Topological Magnetic Textures near Room Temperature in Quantum Magnet TbMn6Sn6

“…It is found that the long-range helical order could be linked to the Fermi surface in Weyl semimetal, topological insulators. [57][58][59][60][61] According to theoretical calculations, the topology of skyrmions can give rise to the topology in the electronic band structure and hence the quantized Hall effect when the Fermi surface is parked in the topological gap. [62] The observation of a skyrmion lattice in this work, together with the recent discovery of electronic topology in TbMn 6 Sn 6 , endows Kagome magnets as an ideal platform to study the rich interplay between topology, magnetism, and electronic properties.…”