Spin Valves as a Tool for Studying Helicoidal Magnetism

Exchange-biased nanostructures of the “spin valve” type, which include an additional layer of the rare-earth metal dysprosium, are made by magnetron sputtering. Temperature variations in the magnetotransport properties of the spin valves are used as an indicator of change in the magnetic state of the dysprosium nanolayer. Information on the formation of unidirectional magnetic anisotropy at the CoFe/Dy interface upon the transition through Néel temperature of dysprosium is obtained. It is shown that the antiferromagnetic phase in the polycrystalline dysprosium layer has noncollinear magnetic ordering. The temperature dependence of the angle between the directions of the magnetic moments at the dysprosium-layer boundaries is determined. The change in this angle observed in the entire temperature region of the existence of helicoidal ordering in dysprosium reflects the change in the period of the magnetic helicoid in dysprosium with temperature. Thus, a new method for studying chiral magnetics is proposed, in which the indicator of the helicoidal magnetic state is a spin valve possessing giant magnetoresistance, containing a layer of the helimagnet under investigation.