Magnetoelastic properties of Co/Pd nanomultilayer films

Abstract

PACS 68.65.+g, 75.70.Cn, 75.80.+q The magnetoelastic properties of (6 Å Co/20 Å Pd) 6 nanomultilayer films have been investigated using an ultrahigh vacuum (UHV) in situ stress and magnetoelastic coupling (MEC) constant measurement system. In situ stress measurement reveals that stress existing in the Pd sublayers is tensile up to the second Pd sublayer deposition and it gradually changes to compressive after the deposition of the third Pd sublayer. Interestingly, the MEC constant of the Co/Pd nanomultilayer continuously increases with increasing Pd layer thickness from 0 to 20 Å in the sixth Pd sublayer. It is found that the evolution of the MEC constant is intimately related with the film strain rather than interface formation, and second-order strain correction is necessary to describe the dependence of the MEC constant on the Pd thickness.1 Introduction Interest in ultrathin ferromagnetic films has grown enormously over the last decade, in part because of their novel physical properties and in part because of their diverse technological applications [1 -3]. One of the important issues in the area of ultrathin ferromagnetic films is their magnetoelastic property, since the magnetoelastic property could provide a new way to control the spin orientation and to enhance new magnetic anisotropy in magnetic devices [4][5][6]. Recent studies on magnetoelastic coupling (MEC) of ultrathin films show that MEC of ultrathin films can be drastically changed at the film interface compared to the bulk. Thus, in addition to the bulk MEC, interface alloy formation or the existence of strain due to the lattice mismatch at the interface is generally introduced to explain the behaviour of MEC near the film interface or surface. However, it is still unclear which mechanism plays a key role in MEC of ultrathin ferromagnetic films.Co/Pd magnetic nanomultilayers, which are artificially grown periodic layered structures of alternating Co and Pd materials, are some of the most promising prospective candidates for the next generation of high-density magnetic and magneto-optical (MO) recording media, due to their novel magnetic and MO properties. Many studies have been carried out on the magnetic and MO properties of Co/Pd systems, but very little work has been done on the magnetoelastic properties of Co/Pd nanomultilayers [7 -10]. In this study we investigate the magnetoelastic properties of Co/Pd nanomultilayer films using an in situ stress/MEC constant measurement system.

Controlling the magnetic anisotropy of CoPt∕AlN multilayer films

“…The lattice mismatch between Co and the noble metals can be as large as 10%; this will inevitably causes elastic strain in both layers when they were grown epitaxially. 8 They also found that the magnetoelastic coupling constant ͑B 2 ͒ showed an oscillatory change; it increased after the deposition of Pd layer and decreased when the next Co layer was deposited. Chappert and Bruno suggested a magnetoelastic surface anisotropy originated from the mismatches between Co and other metals ͑Au and Cu͒, which results in either a homogeneous strain inside the Co layer in the case of pseudomorphic growth or a 1 / t ͑t, thickness of Co layer͒ dependent strain when the mismatch is relaxed by the introduction of interfacial dislocations.…”