Abstract
The fundamental important and technologically widely employed exchange bias effect occurs in general in bilayers of magnetic thin films consisting of antiferromagnetic and ferromagnetic layers where the hard magnetization behavior of an antiferromagnetic thin film causes a shift in the magnetization curve of a soft ferromagnetic film. The minimization of the single magnetic grain size to increase the storage density and the subsequent demand for magnetic materials with very high magnetic anisotropy requires a system with high HEB. Here we report an extremely high HEB of 4 Tesla observed in a single amorphous DyCo4 film close to room temperature. The origin of the exchange bias can be associated with the variation of the magnetic behavior from the surface towards the bulk part of the film revealed by X-ray absorption spectroscopy and X-ray magnetic circular dichroism techniques utilizing the bulk sensitive transmission and the surface sensitive total electron yield modes. The competition between the atomic exchange coupling in the single film and the Zeeman interaction lead to an intrinsic exchanged coupled system and the so far highest exchange bias effect HEB = 4 Tesla reported in a single film, which is accommodated by a partial domain wall formation.
Highlights
The fundamental important and technologically widely employed exchange bias effect occurs in general in bilayers of magnetic thin films consisting of antiferromagnetic and ferromagnetic layers where the hard magnetization behavior of an antiferromagnetic thin film causes a shift in the magnetization curve of a soft ferromagnetic film
The origin of the exchange bias can be associated with the variation of the magnetic behavior from the surface towards the bulk part of the film revealed by X-ray absorption spectroscopy and X-ray magnetic circular dichroism techniques utilizing the bulk sensitive transmission and the surface sensitive total electron yield modes
The competition between the atomic exchange coupling in the single film and the Zeeman interaction lead to an intrinsic exchanged coupled system and the so far highest exchange bias effect HEB = 4 Tesla reported in a single film, which is accommodated by a partial domain wall formation
Summary
In amorphous DyxCo100−x the magnetic configuration is determined by the competition between the magnetic atomic exchange interaction and the Zeemann interaction. The significantly lower value found here in the alloy indicates that the magnetic moments of Dy are not completely aligned along the applied magnetic field direction since the XMCD method is only sensitive to the moments projection along the magnetic field direction This may be explained by the formation of a cone spin structure of Dy as already mentioned before and account for the reduction of MCz o at low temperatures due to the strong antiferromagnetic coupling between Co and Dy. Temperature dependent magnetic hysteresis loops were recorded at the photon energies where the XMCD signals for both elements Dy (E = 1298.4 eV) and Co (E = 778 eV) were largest. For both series of hysteresis loops the temperature dependent transition from the dominate Dy to the dominate Co magnetic state is observed, the saturation behavior shows clear differences in the bulk and surface part, around the compensation temperature
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