muSR investigation of magnetism and magnetoelectric coupling in Cu2OSeO3

TL;DR

This study uses muon spin rotation to investigate the magnetic properties and potential magnetoelectric coupling in Cu2OSeO3, revealing ferrimagnetic order below 57 K and hints of electric field influence on magnetic behavior.

Contribution

It provides detailed muSR measurements of magnetism and evidence for magnetoelectric coupling in Cu2OSeO3, highlighting the critical behavior near the transition temperature.

Findings

Ferrimagnetic order below 57 K with internal magnetic field of 85.37 mT.

Magnetic order parameter follows a 3D magnetic system behavior.

Possible electric field effect on magnetic field of about -0.4 mT.

Abstract

A detailed zero and transverse field (ZF&TF) muon spin rotation (muSR) investigation of magnetism and the magneto-electric coupling in Cu2OSeO3 is reported. An internal magnetic field B_int(T=0) = 85.37(25) mT was found, in agreement with a ferrimagnetic state below Tc = 57.0(1) K. The temperature dependence of the magnetic order parameter is well described by the relation B_int = B(0)(1-(T/Tc)^2)^b with an effective exponent b = 0.39(1) which is close to the critical exponent B ~ 1/3 for a three dimensional (3D) magnetic system. Just above Tc the muon relaxation rate follows the power low \lambda (T)\propto (T/Tc - 1)^\omega with \omega = 1.06(9), which is characteristic for 3D ferromagnets. Measurements of B_int(T) with and without an applied electrostatic field E = 1.66 x 10^5 V/m suggest a possible electric field effect of magnitude \Delta Bv = Bv(0 V)-Bv(500 V) = - 0.4(4) mT.