MnWO4, calorimetric study of the bifurcated antiferromagnetic anomaly

Abstract

The heat capacity of a powdered MnWO4 sample has been measured from 5–350 K. The data show three anomalies below 20 K: a small peak at 6.8±0.1 K, then two large sharp peaks at 12.57±0.05 and 13.36±0.05 K. The magnetic entropy was measured as R ln 6. The data between 5 and 11.5 K obeys a power law dependence Cmag=ATB where B=1.73. The sharp double peak is similar to the bifurcated anomaly in MnCl2 which originates from two distinct antiferromagnetic phases, reported by R. B. Murray et al. The double anomaly is discussed in terms of the superexchange properties of MnWO4.