Large magnetic-field-induced strain at the magnetic order transition in triangular antiferromagnet AgCrS₂

Strain induced by a magnetic field is a common phenomenon for ferromagnets, but few antiferromagnets show large strain induced by a magnetic field. On the basis of linear strain measurements of sintered samples of triangular antiferromagnet ACrS₂ (A = Cu, Ag, and Au) in magnetic fields up to 9 T, the AgCrS₂ sample was found to show a large strain, yielding a large volume change over 700 ppm, which is one of the largest volume changes measured to date for an antiferromagnet. This large strain appeared only at the Néel temperature of 42 K and was not restored to its initial state when the applied magnetic field was decreased to zero; however, it was initialized by cooling the sample to far below the Néel temperature. These results suggest that the coexistence of magnetically ordered and paramagnetic phases at the first-order phase transition plays an important role. AuCrS₂ showed a magnetic field-induced strain with similar features although it was smaller than that in AgCrS₂.