Magnetoelectric Effects in Cr2O3 and (Cr2O3)0.8· (Al2O3)0.2

Abstract

Magnetic field induced magnetoelectric (ME) effects in Cr₂O₃ and (Cr₂O₃)_0.8·(Al₂O₃)_0.2 have been examined with an ac method as a function of temperature and magnetic field. The ME effect parallel to the c axis reverses in sign at low temperatures for both materials, and is linear in H for all temperatures up to the spin‐flop field H_C after which the ME effect approaches zero. The temperature dependence of the extrema of (dE/dH) vs H leads to a measure of H_C vs T which agrees with earlier antiferromagnetic resonance and magnetic moment data in similar materials. Complete reversibility of the ME effect is observed when the magnetic field exceeds H_C and then returns to lower values, thus demonstrating a stable memory of the domain distribution introduced during magnetic annealing. Brief remarks are made on the angular dependence of the ME effect, and indications of nondiagonal contributions in the vicinity of H_C are mentioned.