Very large magnetoresistance effects induced by antiparallel magnetization in two ultrathin cobalt films

Abstract

Magnetoresistance (MR) and magnetization measurements by SQUID have been performed on Au/Co.Au/Co/Au multilayers in which the two ultrathin cobalt films have perpendicular magnetizations and different coercive fields Hc1 and Hc2 due to their different thicknesses. The two Co layers are magnetically uncoupled, as shown by their well separated square hysteresis loops. The MR exhibits a plateau for magnetic fields H such as Hc1<H<Hc2, giving antiparallel orientation of their magnetization. The δR/R value is 1.4% at 300 K and 6% at 4.2 K. These experiments confirm the mechanism of spin-dependent diffusion at the interfaces leading to an increase of the resistance when the two magnetic layers have antiparallel magnetizations.

Inverse giant magnetoresistance (invited)

“…The MR curves have the plateau shape usual for two F films with rectangular magnetization loops and different coercivities. 21,22 While the GMR of Fe/Au/Co, Fig. 6͑a͒, is normal ͑i.e., the largest resistance corresponds to the antiparallel arrangement of the magnetization directions͒, the GMR of Fe 1Ϫx V x /Au/Co is inverse, Figs.…”

Effects of interfacial roughness on the magnetoresistance of Co/Cu multilayers

“…It was first observed in Fe/Cr superlattices [1] with antiferromagnetic coupling between adjacent Fe layers and subsequently found in other metal/metal multilayers with or without antiferromagnetic coupling [2,3]. In particular, sputtered Co/Cu multilayers exhibit the largest magnetoresistance (MR) value and a well defined oscillatory exchange coupling at room temperature [4].…”

Bi surfactant effects of Co/Cu multilayered films prepared by sputter deposition

“…Among the many combinations of film and substrate materials, considerable attention has been paid to the growth of metallic thin films since the discovery of the fascinating properties of metallic multilayers, for example, perpendicular magnetic anisotropy (PMA) [1], giant magnetoresistance (GMR) [2], and the oscillatory behavior of interlayer magnetic coupling [3]. As observed in some metallic films, it is well known that these properties are strongly associated with the sharpness of the interface and the quality of the epitaxy.…”