Dresden 2009 – scientific programme
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MA: Fachverband Magnetismus
MA 8: Magnetic Coupling Phenomena / Exchange Bias
MA 8.11: Talk
Monday, March 23, 2009, 17:45–18:00, HSZ 401
Role of interface alloying on the exchange bias in Fe/Cr bilayers — •Syed Rizwan Ali, Muhammad Bilal Janjua, Marian Fecioru-Morariu, Coen J. P. Smits, and Gernot Güntherodt — Physikalisches Institut (IIA), RWTH Aachen University, 52056 Aachen, Germany
Exchange bias (EB) in polycrystalline Fe/Cr bilayers has been investigated for either molecular beam epitaxy (MBE) grown or sputtered samples. The EB field (HEB) in both series of samples changes its sign as a function of temperature. This zero crossing temperature (T0) was found to increase with the thickness of the Cr layer. The positive part of the HEB shows a maximum and then decreases with temperature up to the blocking temperature of the Cr film. The coercive field HC was also found to vary in close correlation with HEB, exhibiting a maximum near T0. The results are explained by considering a chemically interdiffused Fe/Cr interface, where the interface alloying between Fe and Cr drives Cr into a spin glass (SG) phase. The interfacial exchange interaction between the SG and the ferromagnet is found to be responsible for the observed temperature dependence and sign change of HEB in our samples. HEB of samples containing the intentionally deposited Cr-Fe SG alloy underneath the Fe overlayer show all the features observed in our Fe/Cr bilayer samples, thereby corroborating our arguments.