Charge-order melting and magnetic phase separation in thin films of Pr0.7 Ca0.3 MnO3.

Abstract

We investigate the effect of strain on the phenomenon of charge-order melting, that is the transformation of a charge-ordered insulating state to a metallic state under the influence of a magnetic field (the melting field) in thin films of Pr0.7 Ca0.3 MnO3 grown on various substrates. We find that unstrained films grown on SrLaGaO4 behave quite similar to bulk material, but that strained films grown on SrTiO3 and NdGaO3 show hugely increased melting fields. Strain relaxation by postannealing again leads to bulklike behavior. In this material the antiferromagnetic charge-order phase can coexist with a ferromagnetic insulating state. Magnetization measurements, where we demonstrate the presence of exchange bias effects, show that this is also the case in the strained films. We argue that the phase mixture in the strained films is more difficult to melt than in the unstrained case. © 2009 The American Physical Society.