Magnetic reversal in Dy-doped DyF e 2 / YF e 2 superlattice films

Reversible magnetic exchange springs can be formed in the magnetically soft YFe2 layers of epitaxial DyFe2/YFe2 multilayer films. Here we show that the insertion of just two monolayers of DyFe2, placed directly in the middle of the YFe2 layers, brings about substantial changes. Results are presented for a Dy-doped (110)-oriented [DyFe2(60 angstrom)/YFe2(120 angstrom)/DyFe2(8 angstrom)/YFe2(120 angstrom)] 15 multilayer film, measured at 100 K in fields of up to similar to 10 T. Using bulk magnetometry, micromagnetic modeling, and Dy-specific x-ray magnetic circular dichroism, it is shown that Dy doping substantially increases the number of spin states available to the system. Altogether 12 distinct spring states are identified which bring additional complexity to the magnetic reversal process. In particular, the exchange springs are no longer reversible, exhibitingmagnetic exchange-spring collapse. Full and partial magnetic loops are presented for fields applied along the in-plane easy [001] axis and the in-plane hard [(1) over bar 10] axis. In particular, it is demonstrated that exchange-spring collapse is sharpest when the field is applied along a hard in-plane [(1) over bar 10] axis.