Application of SQUID Magnetometer to the Measurement of Magnetoelectric Effect in Cr₂O₃

Abstract

The use of a SQUID magnetometer in precise measurement of magnetoelectric susceptibilities of Cr2O3 from 1.6 to 270 K is reported. The sensitivity of the magnetometer was about 10-8 emu. A static measurement sweeping the applied electric field provides an easy method to confirm the sign or the linearity of the response. After parallel magnetoelectric cooling along the c axis, the following values were determined: α//max=23×10-6, α//4.2K=-1.2×10-6, α⊥4.2K=-7.0×10-6 cgs/g. The sign of α// changed at 87 K. The technical points of the measurement are discussed and the present results are compared with previous data. An unusual temperature dependence of α discovered in one particular crystal is also reported.