Local structure, transport, and rare-earth magnetismin the ferrimagnetic perovskiteGd0.67Ca0.33MnO3s

Abstract

Bulk, single crystal, and metal-organic chemical-vapor deposition thin-film samples of ${\mathrm{Gd}}_{0.67}$ ${\mathrm{Ca}}_{0.33}$ ${\mathrm{MnO}}_{3}$ were prepared and examined for their electrical, magnetic, and structural properties. ${\mathrm{Gd}}_{0.67}$ ${\mathrm{Ca}}_{0.33}$ ${\mathrm{MnO}}_{3}$ 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 ${\mathrm{Gd}}_{0.67}$ ${\mathrm{Ca}}_{0.33}$ ${\mathrm{MnO}}_{3}$ is consistent with small polaron hopping at high temperatures (up to 1100 K), and possibly by a different mechanism at low temperatures.