Heusler alloys with bcc tungsten seed layers for GMR junctions

Highlights: • Perpendicular anisotropy in Heusler alloys without an MgO interface. • This anisotropy is maintained in layers thicker than 10 nm. • Layer thickness dependent switching gives spin-valve behaviour without exchange bias. We demonstrate that polycrystalline Co₂FeSi Heusler alloys films can be grown with perpendicular anisotropy without the use of an MgO interface. By heating the substrate to 400 °C prior to deposition and using a tungsten seed layer perpendicular anisotropy is induced in the Heusler layer. This is maintained as the thickness of the Co₂FeSi is increased up to 12.5 nm. The layers with thickness dependent coercivity can be implemented into a giant magnetoresistance structure leading to spin-valve behaviour without the need for an exchange biased pinned layer.