Superlattices of magnetoresistive Ca- and Sr-doped manganese perovskites: Interface effects

Abstract Epitaxial superlattices of La 0.7 Ca 0.3 MnO 3 and La 0.7 Sr 0.3 MnO 3 (LCMO/LSMO) N , grown on SrTiO 3 , were obtained by the sputtering technique with the same overall thickness (57 nm) but different number of bilayers ( N = 9 , 12 , 17 , 35 ). The resulting T c (around 292 K) is unexpectedly high and close to the LSMO film T c (305 K). The measured coercive field and saturation magnetization are identical in all of them indicating that interfaces are not playing a direct role in the ferromagnetic interaction, but the volume fraction of paramagnetic Mn increases with the number of interfaces (2 N ). The MR and residual resistivity behaviors are consistent with the presence of paramagnetic Mn at the interfaces and the narrowing of the magnetic domain walls. At room temperature a high low-field-MR ratio is obtained, about 1% at 500 Oe, but no further increase is detected increasing the number of interfaces.