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Highlights • The effects of ferro-elastic domains of LaAlO 3 substrate on the magnetization reversal and magnetic anisotropy of cobalt thin film are studied. • Domain wall pinning along the twin boundary is observed. • Blocked state and single domain state are observed in the alternate region of twins. 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. [ABSTRACT FROM AUTHOR]

The present work reports the preparation of 5  μ m wide and 10  μ m grating periodicity patterned [ F e ( 2.0 n m ) / P t ( 2.5 n m ) ] X 10 multilayer and its thermal annealing behavior. Intermixing across the Fe and Pt layers is observed with vacuum annealing at 650 K resulting in the formation of disordered face centered cubic (FCC) and ordered L 1 0 face centered tetragonal (FCT) FePt phases. The longitudinal magneto-optical Kerr effect (L-MOKE) hysteresis loop, measured from the single 5  μ m FePt stripe shows double loop behavior indicating the presence of two magnetic phases, one with the low coercivity ( H C ) and the second one with the higher H C values. This could be due to the presence of disordered FCC and ordered L 1 0 FCT phases of FePt, known to be soft and hard magnetic phases. Conversion electron M ö ssbauer spectroscopy of the annealed sample shows the presence of FCC and FCT FePt phases corroborating the x-ray diffraction and MOKE measurements. The hysteresis loop of the soft phase shows the exchange bias effect with the remnant state of the hard magnetic phase as initial condition akin to the exchange bias as observed in conventional ferromagnetic - antiferromagnetic bilayers. [ABSTRACT FROM AUTHOR]

Magnetization reversal and magnetic microstructure of top soft magnetic layer (Fe) in exchange spring coupled L1 0 FePt/Fe is studied using high resolution Kerr microscopy. With remnant state of the hard magnetic layer (L1 0 FePt) as initial condition, magnetization loops along with magnetic domains are recorded for the top soft magnetic layer (Fe) using Kerr microscopy. Considerable shifting of Fe layer hysteresis loop from center which is similar to exchange bias phenomena is observed. It is also observed that one can tune the magnitude of hysteresis shift by reaching the remanent state from different saturating fields ( H SAT ) and also by varying the angle between measuring field and H SAT . The hysteresis loops and magnetic domains of top soft Fe layer demonstrate unambiguously that soft magnetic layer at remanent state in such exchange coupled system is having unidirectional anisotropy. An analogy is drawn and the observations are explained in terms of established model of exchange bias phenomena framed for field-cooled ferromagnetic - antiferromagnetic bilayer systems. [ABSTRACT FROM AUTHOR]