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Magnetization-reversal processes in an ultrathin Co/Au film
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Edité par CCSD ; American Physical Society -
International audience. Magnetization-reversal processes in a ferromagnetic cobalt film structure (Au/Co/Au), with perpendicular anisotropy, were investigated by magneto-optical magnetometry and microscopy. In the considered ultrathin Co film, the magnetization reversal between the two Ising-spin equilibrium states is dominated by the domain-wall motion mechanism. We focused our studies on processes initiated from a given demagnetized state. Starting from a magnetically saturated state generated under a large field (Formula presented), applied perpendicular to the film, this demagnetized state is created through magnetic aftereffects in a field (Formula presented) antiparallel but smaller than (Formula presented) and applied during a selected time. Direct ((Formula presented)) and indirect ((Formula presented)) magnetization processes are then studied from this state for application of the field parallel and antiparallel to (Formula presented), respectively. The dynamics of the magnetization reversal is much faster for the (Formula presented) process since it is initiated from a quasihomogeneous 'Swiss cheese' domain state with small nonreversed regions. The magnetic accommodation phenomenon is studied, and a domain-shape memory effect evidenced. A theoretical analysis of the dynamics of magnetization processes is proposed, starting from the model of a patchy inhomogeneous media with a realistic distribution of local coercivities. The pertinent parameters for calculations are deduced from our experimental data using appropriate analytical expressions of the magnetic relaxation time and domain-wall velocity under a field. Computer simulations using these parameters reproduce well the time evolution of the magnetic domain pattern and different magnetization curves both for (Formula presented) and (Formula presented) magnetization processes.
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