Effect of ferro-elastic twin domains of LaAlO3 substrate on the magnetic anisotropy and the magnetization reversal process of cobalt thin film

Abstract

Abstract Present work reports the effects of ferroelastic domains (FE) on the magnetic properties of top magnetic layer. Cobalt film of 15 nm is deposited using electron beam evaporation technique on single crystalline LaAlO 3 (0 0 1) (LAO) substrate which consists FE structural twin domains. LAO substrate is in-situ heated above its FE transition temperature and cooled to room temperature before depositing cobalt film of 15 nm. Textured growth of cobalt film is observed in-situ from reflection high energy electron diffraction (RHEED) patterns. The presence of FE structural twins in LAO substrate is confirmed from the X-ray reciprocal space mapping measurements. From the optical polarization microscopy, it is observed that the different regions consist different modulations viz., lamellar like and square-like structures in LAO substrate. The magnetic anisotropy and magnetization reversal is studied ex-situ using magneto-optical Kerr effect (MOKE) microscopy with different spatial resolutions. The analysis of azimuthal variation of coercivity ( H C ) shows the superposition of two-, four- and six- fold anisotropy contribution at different regions of the sample. Twofold anisotropy and weak sixfold anisotropy may due to magneto-crystalline anisotropy, whereas the fourfold anisotropy might be coming because of square-like modulations of the substrate. Moreover, MOKE microscopy reveals the domain wall pinning along the twin boundaries (FE) due to which magnetization reversal is proceed by three distinct mechanisms when field is applied away from easy axis of magnetization and lamellar pattern. As a consequence of this, magnetization reversal proceeds by ‘labyrinth switching’ and abrupt magnetic domain wall switching within individual FE domains.