Impact of interfacial magnetism on magnetocaloric properties of thin film heterostructures

Polarized neutron reflectometry was used to determine the depth profile of the magnetic moment per Gd atom, m(Gd), in a Gd(30 nm)/W(5 nm) multilayer. Despite sharp interfaces observed by transmission electron microscopy, m(Gd) is systematically suppressed near the Gd-W interfaces. Because the peak magnetic entropy change is proportional to m(Gd)(2/3), this results in a reduction of the maximum achievable magnetocaloric effect in Gd-W heterostructures. By extension, our results suggest that creating materials with Gd-ferromagnet interfaces may increase the m(Gd) relative to the bulk, leading to enhanced magnetocaloric properties. (C) 2011 American Institute of Physics. [doi:10.1063/1.3555101]