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

Abstract

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.

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Cited by in corpus (4)

• Spin wave stiffness and damping in a frustrated chiral helimagnet Co${}_8$Zn${}_8$Mn${}_4$ as measured by small-angle neutron scattering
• Direct observation of the exchange anisotropy in the helimagnetic insulator Cu${}_2$OSeO${}_3$
• Probing Short-Range Correlations in the van der Waals Magnet CrSBr by Small-Angle Neutron Scattering
• Enhanced skyrmion metastability under applied strain in FeGe