Abstract:
The existence of nonergodic ground states is considered as a precursor to a first-order long-range magnetostructural transformation. Mn sub(3)Ga sub(0.45)Sn sub(0.55)C lies compositionally between two compounds, Mn sub(3)GaC and Mn sub(3)SnC , undergoing first-order magnetic transformation. However, Mn sub(3)Ga sub(0.45)Sn sub(0.55)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 Mn sub(3)Ga sub(0.45)Sn sub(0.55)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.
