Modelling magnetic exchange springs in 1D, 2D, and 3D

Abstract

1D models of magnetic multilayers, with alternating hard and soft layers, are extended to 2Dand 3D, and presented within a common framework of nearest neighbour interactions. Using2D calculations, it is shown that the properties of magnetic exchange springs can be changedsignificantly by patterning the hard pinning layers. But, in certain cases the bending fieldBB is not significantly altered, even when half the pinning layer is removed. 3D calculations are usedto probe the effects of defects on the properties of magnetic exchange springs, using epitaxialDyFe2/YFe2 superlattices as an example. It is shown that point defects such as Fe vacancies have littleeffect on the bending field transition. This is in marked contrast to the 1D model,where an Fe vacancy cuts the magnetic exchange spring into two. Finally, it isdemonstrated that significant changes in the properties of magnetic exchangesprings can be engineered, by placing rare-earth ions in the centre of the softYFe2 springs. A new phenomenon, exchange spring collapse, is predicted.