Temperature dependence of the magnetic domain structure in disordered FePt films

J. M. GUZMÁN; NADIA ÁLVAREZ; MARCELO VÁSQUEZ MANSILLA; JAVIER GÓMEZ; ALEJANDRO BUTERA

Parma

Conferencia; Joint European Magnetic Symposia (JEMS 2012); 2012

We have observed a transition in the magnetic domain structure of FePt thin films when the film thickness or the temperature is varied. These samples have a Q-factor Q = 2K^/M ~ 0.3, and a transition between planar to stripe-like domains occurs for film thicknesses above 30 nm. The critical  thickness depends on Q, so that a change in the domain structure is expected when Q changes. Due to the different thermal expansion of FePt and Si a reduction in Q is predicted when the temperature is lowered. From M vs. H loops measured at different temperatures below 300 K, we have effectively observed a change in the coercive field which can be associated to a transition from stripe-like to in-plane domains. The transition temperature range is broad, indicating a gradual variation between the two magnetic configurations, but changes systematically with film thickness, consistent with an interfacial induced strain.