Local structure, transport, and rare-earth magnetismin the ferrimagnetic perovskites

Bulk, single crystal, and metal-organic chemical-vapor deposition thin-film samples of (Formula presented) were prepared and examined for their electrical, magnetic, and structural properties. (Formula presented) is ferrimagnetic with a transition temperature between 50 and 80 K and a compensation temperature of about 15 K. A molecular field model with a ferromagnetic manganese sublattice antiparallel to the gadolinium sublattice qualitatively explains the magnetism data. A large high-field susceptibility is observed at 5 K, suggesting a sublattice rotation. The resistivity and the magnetoresistance show no anomaly near the ferrimagnetic transition. There is no noticeable change in the structure, as seen from the x-ray-absorption fine structure between 40 and 69 K, indicating that there is no structural discontinuity across the paramagnetic insulator to ferromagnetic insulator phase boundary. The resistivity of (Formula presented) is consistent with small polaron hopping at high temperatures (up to 1100 K), and possibly by a different mechanism at low temperatures.