Spin configurations and negative coercivity in epitaxially grown DyFe2/YFe2 superlattices

Molecular beam epitaxial methods have been used to grow single crystal Laves phase DyFe2/YFe2 superlattice samples with a (110) growth direction. In particular, the magnetic properties of the YFe2 dominated multilayer samples [wDyFe(2)/4wYFe(2)] x N with w = 20, 30, 40, 45, 50, and 55 Angstrom are presented and discussed. In principle, the multilayer films should possess similar magnetic properties because they are all nominally Dy0.2Y0.8Fe2. However, it is shown that their magnetic properties depend strongly on the thickness of the DyFe2 layers w. Those films with w greater than or equal to 45 Angstrom possess negative coercivities, while those with w less than or equal to 40 Angstrom are positive. It is argued that this behavior can be understood in terms of a strong increase of the intrinsic coercivity of the DyFe2/YFe2 superlattice, taken as a whole, as w is reduced. For w less than or equal to 40 Angstrom almost none of the DyFe2 moments can be flipped over in the available field range (12 T). (C) 2001 American Institute of Physics.