Carbon deficiency-induced changes of structure and magnetism of Mn₃SnC

Crystal structure, magnetoelastic coupling, magnetization and magnetocaloric effects of Mn₃SnC_0.94 and Mn₃SnC_0.81 were investigated. Temperature-dependent high-resolution X-ray diffraction measurements showed that a larger carbon deficiency of Mn₃SnC_0.81 reduces lattice distortions more significantly than it reduces the lattice parameter. Resonant ultrasound spectroscopy measurements showed that the larger carbon deficiency has no effect on the lattice stiffening across a ferromagnetic transition, whereas it reduces the lattice softening across a low-temperature transition. Magnetic measurements showed that the larger carbon deficiency doubles high-field magnetization and improves the refrigeration capacity. It is suggested that the larger carbon deficiency of Mn₃SnC_0.81 weakens antiferromagnetic interactions more significantly than it enhances ferromagnetic interactions. However, the magnetocaloric effect of each sample includes a contribution from the lattice entropy change, which is not sensitive to the carbon deficiency.