Experimental Evidence of a change of Exchange Anisotropy Sign with Temperature in Zn-Substituted Cu2OSeO3

Autor: Moody, S. H., Nielsen, P., Wilson, M. N., Venero, D. Alba, Štefančič, A., Balakrishnan, G., Hatton, P. D.
Rok vydání: 2021
Předmět:
Druh dokumentu: Working Paper
DOI: 10.1103/PhysRevResearch.3.043149
Popis: We report small-angle neutron scattering from the conical state in a single crystal of Zn-substituted Cu2OSeO3. Using a 3D vector-field magnet to reorient the conical wavevector, our measurements show that the magnitude of the conical wavevector changes as a function of crystallographic direction. These changes are caused by the anisotropic exchange interaction (AEI), whose magnitude transitions from a maxima to a minima along the <111> and <100> crystallographic directions respectively. We further find that the AEI constant undergoes a change of sign from positive to negative with decreasing temperature. Unlike in the related compound FeGe, where similar behaviour of the AEI induces a reorientation of the helical wavevector, we show that the zero field helical wavevector in (Cu0.98Zn0.02)2OSeO3 remains along the <100> directions at all temperatures due to the competing fourth-order magnetocrystalline anisotropy becoming dominant at lower temperatures.
Databáze: arXiv