Temperature dependent domain investigations on exchange biased NiFe/IrMn and CoFe/IrMn systems

摘要

For tunneling magnetoresistance (TMR) sensor applications, the magnetic properties of both, the soft magnetic detection layer and of the hard magnetic reference layer, have to be optimized. For the reference layer either artificial antiferromagnet (AAF) subsystems, exchange biased magnetic layers or a combination of the two are commonly used. In this work we studied the magnetic microstructure and magnetization processes of sputtered IrMn/Permalloy, IrMn/CoFe and IrMn/CoFe-AAF systems by Kerr microscopy and magneto-optical magnetometry in a temperature range between 0° and 400°C. A vacuum heating stage in the microscope allowed the in-situ setting of exchange bias by heating and cooling through the blocking temperature. We found that local decoupling phenomena occur over a rather wide temperature range, showing clear dependencies on the material, the direction of the applied field and the thickness of the IrMn antiferromagnetic layer.