Magnetic switching along hard-axes in Er-doped DyFe₂/YFe₂ thin films

Full text: Molecular-beam-epitaxial (MBE) grown [DyFe₂ /YFe₂] multilayer films form an ideal model system for the study of magnetic exchange springs. Here the DyFe₂ (YFe₂) layers are magnetically hard (soft), respectively. Thus, in the presence of a magnetic field exchange springs form in the YFe₂ layers. Recently, it has been shown that placing small amounts of Er into the centre of the YFe₂ springs generates substantial changes in magnetic behaviour. In particular, (i) the number of exchange-spring states is increased dramatically, (ii) the resulting domain wall states are not simply describable either as Néel or Bloch walls, (iii) the Er and Dy magnetic loops differ strikingly, and (iv) the phenomenon of Er-induced magnetic exchange-spring collapse. Here we present results for Er-doped (110)-oriented [DyFe₂ (60 Å)/ YFe₂ (240 Å)]₁₅ multilayer films, at 100 K in fields of up to ±14 T. In particular, results are contrasted for fields applied along seemingly equivalent hard-magnetic [110]-type axes. MBE grown cubic Laves thin films offer the unique feature of allowing the magnetic field to be applied along a hard out-of-plane [110]-axis (the growth axis), and a similar hard in-plane [^Ί10]-axis. Differences are found and attributed to (i) the ϵ_xy strain term induced during crystal growth, and (ii) the long-range dipole-dipole interaction, calculated using a model recently developed for thin films. In particular, the out-of-plane [110] Er-results reveal the existence of a new magnetic exchange spring state, which could only be identified using element-selective x-ray magnetic circular dichroism (XMCD). (author)