Effects of chemical pressure on ferromagnetism and transport properties in La _(0.7-x)Y _xCa _(0.3)CoO _3

摘要

We have investigated the chemical pressure effects, induced by the substitution of smaller ionic radius Y ~(3+) for La ~(3+), on the magnetic and electrical transport properties for the La _(0.7-x)Y _xCa _(0.3)CoO _3 (x = 0, 0.05, 0.1, and 0.15). The magnetization and the Curie temperature T _C decrease sharply as the doping level of Y ~(3+) increases, which indicates that the chemical pressure induced by Y ~(3+)-doping can suppress the ferromagnetism. The transport measurement reveals a chemical pressure-induced increase of the resistivity due to a suppression of e _g-electron hopping. We thought that the effect of Y ~(3+)-doping induced chemical pressure on the ferromagnetic (FM) phase has a similar behavior to that of external pressure. These results imply that the enhancing chemical pressure can suppress the FM phase in La _(0.7-x)Y _xCa _(0.3)CoO _3.