  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 N\'eel 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 N\'eel 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.
