Phase transition and magnetic anisotropy of (La,Sr)MnO3 thin films

Abstract

The magnetic properties and their correlation with the microstructure and electrical transport are investigated in ${\mathrm{La}}_{0.88}{\mathrm{Sr}}_{0.1}{\mathrm{MnO}}_{3}$ films grown on $(100){\mathrm{SrTiO}}_{3}$ single crystal substrates with thickness ranging from 100 to 2500 \AA{}. The ultrathin film $(t=100 \mathrm{\AA{}}\mathrm{})$ has a single ferromagnetic transition (FMT) at ${T}_{c}$ of 250 K, whereas the thicker films exihibit two FMTs, with the main one at a lowered ${T}_{c}$ of 200 K while the minor one around 300 K. Furthermore, a thickness dependent magnetic anisotropy has been found, strongly indicating the existence of strain effect, which is also revealed by the transmission electron microscopy study. The suppressed Jahn-Teller distortion (JTD) by the epitaxial strain, and the recovered JTD due to the strain relexation are suggested to explain the metallic behavior in thin films and the insulating behavior in the thick film $(t=2500 \mathrm{\AA{}}\mathrm{}),$ repectively.