Magnetoresistive Properties of Dy-Based Bottom Spin Valve

Dysprosium-based bottom spin valves with the thickness of the dysprosium layer comparable to the spatial period of the magnetic helicoid were fabricated by magnetron sputtering. Perfect fiber crystal texture was obtained in Dy layer sputtered on Ta underlayer. The inversion of magnetoresistive curves with temperature decreasing is observed. The explanation of these features is based on the paramagnet-antiferromagnet transition in dysprosium nanolayer and on the deformation of helicoidal magnetic structure by an applied magnetic field. It has been determined that at the same temperature and field the smaller is the thickness of the ultra-thin dysprosium layer, the greater is its magnetic moment. The Neel temperature was estimated for dysprosium nanolayer in Ta/Dy/Ta structures where the smallest thickness of the dysprosium layer was 10 nm. It has been revealed that the temperature of transition from paramagnetic to antiferromagnetic state is different in the film regions in which helicoid axis is close to parallel or perpendicular to the film plane.