Cation size and strain effects in La 2/3(Ca 1− x′ Sr x′− x″ Ba x″ ) 1/3MnO 3

Abstract

Based on investigations of metal–insulator transition temperature T m on La 2/3(Ca 1− x′ Sr x′− x″ Ba x″ ) 1/3MnO 3, we point out that considerations based only on the mismatch effect or the strain-field effect cannot provide a reasonable description for the experimental observations. Including two contributions arising from the average A-cation size (〈 r A〉) and the strain-field effect defined by a quantity S=〈( r A 0− r A) 2〉 gives T m varying as T m= T m(〈 r A〉,0)− pS, where T m(〈 r A〉,0) is the transition temperature in the absence of the strain-field effect and the parameter p is estimated to be ∼1.05×10 6 K nm −2. It is shown that the strain-corrected T m shows a behavior expected by the double-exchange mechanism which monotonously increases towards ∼500 K with increasing 〈 r A〉 towards r A 0 (the A-cation size of an ideal cubic perovskite).