Magnetic Anisotropy in La0.7(Sr,Ca)0.3MnO3 Epitaxial Thin Films And Crystals

Abstract

ABSTRACTThe biaxial and uniaxial magnetic anisotropies of epitaxial { 100} oriented La0.7(Sr,Ca)0.3MnO3 films on different substrates and of a sphere-shaped single crystal were measured by torque magnetometry at temperatures ranging from T = 20K to room temperature. In the films the biaxial anisotropy with easy axes <110= dominates and is described by a cubic crystal anisotropy constant ranging up to K1 ≈−104J/m3. The uniaxial anisotropy was |Ku| ≤ 103 J/m3 and is explained by anisotropic stress. In the single crystal the main anisotropy is uniaxial with a hard axis parallel to [ 111], and with an anisotropy constant KR up to 104J/m3. KR was measured in different planes and explained by the rhombohedral lattice distortion. The biaxial anisotropy in the crystal (K1 = −103 J/m3 at T = lOOK) was smaller than in the films. Differences between film and single crystalline behaviour are discussed in terms of crystal structure and lattice constriction.