Magnetic Circular Dichroism in Antiferromagnetic MnF2

Abstract

The magnetic circular dichroism(MCD) properties of antiferromagnetic MnF2 in the 4 T 1(4 G) region have been studied. We show that MCD is a useful technique in furthering our understanding of the spectra of these materials, particularly when complex assisted transitions are involved. Out of the complex band absorption, only a weak electric dipole feature at 18 536 cm−1 and the one‐magnon sideband region exhibit magnetic circular dichroism. We present conclusive evidence that the weak electric dipole transition is a two‐magnon sideband of the pure electronic line E 2 in this manifold. The position and temperature dependence are in good agreement with other two magnon experimental data. The MCD splitting also yields an effective g factor for the two‐magnon sideband which is in good agreement with existing data. We conclude that this three‐center excitation is caused by a zone‐center exciton plus two X 2 zone‐edge magnons. Fitting the observed MCD signal from the one‐magnon sideband region to a calculated line shape gives us an estimate of the effective g factor for zone‐edge magnons in MnF2.