Thermal Expansion and Volume Magnetostriction in Breathing Pyrochlore Magnets LiACr${}_4$X${}_8$ (A = Ga, In, X = O, S)

We report thermal expansion and magnetostriction in breathing pyrochlore magnets LiACr${}_4$X${}_8$ (A = Ga, In, X = O, S) measured by a dilatometric method on sintered samples. All four of these compounds showed a large volume contraction associated with antiferromagnetic order with decreasing temperature. Above the Ne'el temperature, LiGaCr4S8 showed negative thermal expansion, LiInCr4O8 showed positive thermal expansion with concave-downward temperature dependence, and LiInCr4S8 showed positive forced volume magnetostriction. All these phenomena are likely caused by the complex structure-magnetism correlation within the breathing pyrochlore structure with J and J’. These results suggested that breathing pyrochlore magnets are promising for the realization of various volumetric phenomena related to their magnetism not only in the magnetically-ordered phase but also in the paramagnetic phase.