Low-pressure-driven barocaloric effects at colinear-to-triangular antiferromagnetic transitions in Mn3-xPt1+x

A large driving pressure is required for barocaloric effects (BCEs) in intermetallics, usually above 100 MPa. Here, we report barocaloric effects in Mn3-xPt1+xalloys saturated at about 60 MPa, the lowest pressure reported in intermetallics to date. A first-order phase transition occurs from the colinear antiferromagnetic phase to the triangular antiferromagnetic phase as temperature decreases. The transition temperature strongly depends on the composition x, ranging from 331 K for x = 0.18 to 384 K for x = 0.04, and is sensitive to pressure, with dTt/dP up to 139 K/GPa. However, the maximum pressure-induced entropy changes are as small as 13.79 J kg-1 K-1, attributed to the mutual cancellation of lattice and magnetic entropy changes. The small driving pressure and total entropy changes are due to the special magnetic geometric frustration.