Growth and characterization of La2/3Ca1/3MnO3 thin films on ‘silicon on insulator’ substrates

Abstract

La2/3Ca1/3MnO3 thin films have been grown on SrTiO3, LaAlO3, and yttria-stabilized zirconia buffered silicon-on-insulator (SOI) substrates by the pulsed laser deposition technique. While full cube-on-cube epitaxy was achieved on the SrTiO3 and LaAlO3 substrates, a coexistence of the cube-on-cube and cube-on-diagonal epitaxy was observed in the the manganite films on SOI substrates. Besides the intrinsic four-fold magnetocrystalline anisotropy, a uniaxial anisotropy also exists in the films, which is determined by the demagnetization field and the mismatch-induced strain. A tensile strain leads to an easy plane, while a compressive strain favors an easy axis. The different magnetization configurations in the films on different substrates are the reason for their varied transport and magnetic properties. Due to a combined effect of these magnetic anisotropy, the magnetization in the two crystallography domains in the film on SOI tends to lie in the film plane but align in their respective easy axes. There are always large spin angles across the domain boundaries. As a result, a quite large low-field magnetoresistance (LFMR) based on spin-dependent tunnelling was observed. It shows a resistance change of ∼20% at 50 K in a magnetic field ∼700 Oe, which is promising for real applications.