Strong suppression of Curie temperature of spin-polarized ferromagnet La1-xSrxMnO3 by application of dynamic strain

The ferromagnetic state of the spin-polarized ferromagnet La1-xSrxMnO3 is stabilized in the metallic region by strong coupling between localized spins in the t(2g) orbital and conduction electrons in the e(g) orbital. We prepared polycrystalline La1-xSrxMnO3 films (x = 0.15, 0.25, or 0.30) by deposition on an oxidized Si substrate. The three types of La1-xSrxMnO3 films were in the ferromagnetic rhombohedral phase, and their Curie temperatures, T-C, evaluated from the midpoint of ac magnetization, were 305 K, 335 K, and 338 K, respectively. By applying expansion-mode acoustic vibration to the crystal structure of La1-xSrxMnO3, we observed a remarkable decrease (as large as 70 K) in T-C. The applied structural perturbation causes a decrease in the possibility of conduction electron hopping and an increase in the Jahn-Teller distortion. The former is more effective for decreasing T-C than the latter.