Large lattice effects arising from Sc on magnetic and transport properties in La_0.7Ca_0.3Mn_1-xSc_xO₃

Structural, magnetic, and transport properties in La_0.7Ca_0.3Mn_1-xSc_xO₃ have been experimentally investigated. A sensitive response on the magnetic and transport properties to Sc substituting for Mn is observed, demonstrated as a rapid decrease in Curie temperature (T_C) and a remarkable enhancement in magnetoresistance. In the range of x=0–0.03, T_C shifts linearly to a lower temperature with increasing x at a rate of around 37 K for each 1% Sc³⁺ doping. The data of saturation magnetization show no magnetic coupling between Sc and Mn ions. Mn⁴⁺/Mn content increases from 30.5 to 37.7% when x varies from 0 to 0.1, indicative of the small influence on T_C. Structural refinement reveals a large lattice distortion in the MnO₆ octahedra with Sc doping because of the dopant-size-induced local strain effect. According to the dependence of the tolerance factor on magnetic phase diagram, it is believed that the enhanced doping effects should be ascribed to the additional local strain effect, as well as the size mismatch between A- and B-site ions, caused by the large Sc³⁺ ions in the lattice.