Spin-phonon interaction and mode softening in NiF2

The temperature dependence of the four Raman-active phonons in NiF2 is investigated at temperatures above and below the antiferromagnetic ordering temperature of T-N=73 K. All four modes exhibit distinct anomalies in their intensities and frequencies near T-N due to spin-phonon coupling. The phonon linewidths also exhibit weak anomalies. From the temperature dependences of the phonon frequencies, estimates are made of the spin-phonon coupling coefficients. The B-1g phonon exhibits anomalous mode softening with decreasing temperature from 300 K to T-N. (C) 2002 American Institute of Physics.