Magnetotransport properties of La0.7Sr0.3MnO3/SrTiO3 superlattices

The crystalline structures, magnetisms, and magnetotransport properties of La0.7Sr0.3MnO3/SrTiO3 (LSMO/STO) superlattices and La0.7Sr0.3MnO3 (LSMO) films are studied. The transmission electron microscopy images confirm the sharp interfaces and uniformly continuous layers in superlattices and provide the evidence that the superlattices almost have the same in-plane stress while they have a slight increase of out-of-plane strain in LSMO layers for superlattices with thicker STO layers. For the LSMO/STO superlattices with thicker STO or thinner LSMO layers, the decreases in Curie temperature, magnetization, and effective carrier concentration, accompanied by an enhanced residual resistivity, have been observed. In the magnetotransport study, the temperature dependence of longitudinal resistivity rho(xx)(T), the magnetoresistance ratio (MR) as a function of magnetization M, and the scaling of anomalous Hall coefficient R-s versus longitudinal resistivity rho(xx) are found to follow the behaviors of rho(xx)(T)similar to T-alpha with alpha=2.3-2.5, MR=-C[M/M-s](2) with C=1.45-2.17, and -R-s proportional to(rho(xx))(n) with n=1.55-2.04, respectively, where M-s is the saturation magnetization. Furthermore, the increased alpha, and the decreased C and n for superlattices with thicker STO or thinner LSMO layers, are presented. This study provides insight into the effects of decoupling and magnetic disordering on the physical mechanism of the magnetotransport properties of the LSMO/STO superlattices. Our results demonstrate that the interlayer decoupling increases the influence of disorder effects on the magnetism and dominates the magnetotransport phenomenon in LSMO/STO superlattices, while the strain effect plays a minor role on the magnetotransport properties of the overall samples discussed here.