Selective realignment of the exchange biased magnetization direction in spintronic layer stacks using continuous and pulsed laser radiation
2014
We report on selective realignment of the magnetization direction of the exchange biased ferromagnetic layer in two
different spintronic layer stacks using laser radiation. The exchange bias effect occurs in an
antiferromagnetic/ferromagnetic bilayer system when cooled in an external magnetic field below the Neel temperature
and results in a shift of the ferromagnetic hysteresis loop with increased coercivity. The effect is utilized to pin the
magnetization direction of the reference ferromagnetic layer in spin valve systems. We investigated the realignment of
the pinned magnetization direction in a spin valve system with in plane exchange bias and in a Co/Pt multilayer with
perpendicular exchange bias. The layer stacks were heated above the Neel temperature in a defined lateral area by using
rapidly deflected laser radiation. Two different laser assisted annealing techniques were investigated applying either
continuous or pulsed laser radiation. During laser annealing, the sample was subjected to an external magnetic field in
order to selectively realign the magnetization direction of the pinned ferromagnetic layer. Magnetic structuring was
performed by heating narrow single tracks as well as irradiating single pulses. By using a magneto optical sensor in
combination with a polarization microscope, the magnetic structures have been visualized. After laser annealing of
larger-scaled areas, the exchange bias field strength and the coercive field strength were analyzed using a magneto
optical Kerr effect set up (MOKE). The impact of the processing parameters laser peak intensity, laser pulse duration,
scan speed (continuous wave) and magnetic field strength on the resulting reversed exchange bias field was evaluated.
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