Phase-separated magnetic ground state in Mn3Ga0.45Sn0.55C

The existence of nonergodic ground states is considered as a precursor to a first-order long-range magnetostructural transformation. ${\mathrm{Mn}}₃{\mathrm{Ga}}_0.45{\mathrm{Sn}}_0.55\mathrm{C}$ lies compositionally between two compounds, ${\mathrm{Mn}}₃\mathrm{GaC}$ and ${\mathrm{Mn}}₃\mathrm{SnC}$, undergoing first-order magnetic transformation. However, ${\mathrm{Mn}}₃{\mathrm{Ga}}_0.45{\mathrm{Sn}}_0.55\mathrm{C}$, which crystallizes in a single-phase cubic structure, exhibits more than one long-range magnetic transition. Using a combination of magnetization, ac susceptibility, neutron diffraction, and x-ray-absorption fine-structure techniques, it is shown that, although ${\mathrm{Mn}}₃{\mathrm{Ga}}_0.45{\mathrm{Sn}}_0.55\mathrm{C}$ exhibits long-range magnetic order, it presents a cluster glassy ground state due to formation of magnetically ordered Ga-rich and Sn-rich clusters. The clusters are big enough to present signatures of long-range magnetic order but are distributed in a way that limits interactions between two clusters of the same type, leading to a frozen magnetic state at low temperatures. The main reason for such a cluster-glass state is the difference in the local structure of Mn atoms that find themselves in Ga-rich and Sn-rich clusters.