Magnetocaloric Properties of Thin Film Heterostructures*

In an effort to understand the impact of nanostructuring on the magnetocaloric (MC) effect, we have studied gadolinium in MgO/W(50 {\AA})/[Gd(400 {\AA})/W(50 {\AA})]$_{8}$ heterostructures [Miller et al., J. Appl. Phys. 107, 09A903 (2010)]. The entropy change peaks at a temperature of 284 K with a value of 3.4 J/kg K for a 0--30 kOe field change. Polarized neutron reflectometry was used to determine the depth profile of the magnetic moment per Gd atom, m$_{Gd}$ in a Gd/W multilayer. Our results suggest that creating materials with Gd-ferromagnet interfaces may increase the m$_{Gd}$, leading to enhanced MC properties. Therefore SiOx/Fe(50 {\AA})/Gd(300 {\AA})/Fe(50 {\AA}) heterostructures have been investigated.