New Magnetoelectric Effect: Evidence for Spin-Dependent Electrical Polarizabilities from Magnetocapacitance Measurements on n -type Silicon

Magnetocapacitance measurements on a nonpolar paramagnetic system of antiferromagnetically exchange-coupled neutral donors in the temperature range 4.2 to 1.1 K reveal a strongly temperature-dependent coefficient of the H² term much larger in magnitude than the usual weak diamagnetic effect. The new effect arises from the Zeeman effect of the excited triplet spin state of donor pairs and is proportional to the difference between the singlet- and triplet-state polarizabilities. The temperature dependence is like that of the Schottky specific-heat anomaly.