Disorder effects in (LaTb)0.5(CaSr)0.5MnO3 compounds

Abstract

Electrical, magnetotransport, and magnetization measurements have been carried out on half-doped (La0.5−xTbx)(Ca0.38−ySr0.12+y)MnO3 (0.025⩽x⩽0.125; y=0.8x) compounds. The increase in Tb3+ and Sr2+ contents keeps the average A-site ionic radius constant at ∼1.215 Å but introduces increasing size disorder. The insulator-metal transition temperature (Tp) falls from 191 to 107 K and the Curie temperature (TC) falls from 230 to 106 K as x increases from 0.025 to 0.125. Interestingly, with increasing size disorder, the disparity between TC and Tp disappears and magnetoresistance increases around Tp but decreases at low temperatures. This is discussed in the light of phase segregation.