Inverse giant magnetoresistance in rare-earth/transition metal multilayers

¹ E. C. Stoner Laboratory, Department of Physics and Astronomy University of Leeds - Leeds, LS2 9JT, UK
² ISIS, Rutherford Appleton Laboratory - Chilton, Didcot, Oxon, OX11 0QX, UK

Received: 19 August 1999
Accepted: 3 December 1999

Abstract

Giant magnetoresistance (GMR) is observed in multilayered structures with 3d ferromagnetic layers separated by normal metal spacer layers, and is usually a negative magnetoresistance. No GMR has been observed to date in multilayers with solely 4f ferromagnetic layers. Nevertheless, in a hybrid 3d/4f magnetic multilayer of the form an inverse GMR of up to has been measured at 4.2 K. This effect is explained in terms of a spin-engineered configuration of layers which forces the moments of adjacent Co layers to be anti-parallel in a high-field state, and parallel in a low-field state. Since the structure is formed from separate magnetic layers, it has been shown, by varying the order of the layers, that Co/Cu interfaces are essential to the GMR in these types of structures. Although there is no GMR in rare-earth/non-magnetic multilayers, the Dy layers are sufficiently transparent to electrons for the GMR to continue rising as the number of repeat units is increased, up to N = 4.