Structural and magnetic properties of Er thin films and Er/Y superlattices: Magnetoelastic effects

Abstract

Crystalline erbium thin films and Er/Y superlattices with varying Er-layer thicknesses have been grown by molecular-beam epitaxy. The magnetic and structural properties of these samples have been analyzed by x-ray-scattering, bulk magnetization, and neutron-diR'raction techniques.From a comparison of the data for the two systems, the importance of interfacial strain relative to artificial modulation in shaping the magnetic behavior has been determined. Though the basic nature of the erbium magnetic order is not qualitatively altered in either the thin films or superlattices, the conical ferromagnetic phase is suppressed in all of the samples considered. The enhanced critical fields exhibit a systematic dependence on Er-layer thickness. These effects appear to follow directly from the epitaxial basal-plane strain which is measurable in films over 14000 A thick. This strain, along with a "clamping" of the Er thermal expansion to the Y lattice, leads to a reduction of the magnitude of the magnetoelastic energy that drives the ferromagnetic transition. The dependence of the magnetoelastic energy on the epitaxial strain is described by a model which accounts for the elastic coupling of the erbium lattice to the yttrium.

Probing the spiral magnetic phase in 6 nm textured erbium using polarised neutron reflectometry

“…This c-axis extension is consistent with an in-plane contraction and can be reduced, towards the bulk value, by increasing Er film thickness [9]. The addition of a Y buffer layer between the Nb and Er can cause the opposite effect, a contraction in the measured c-axis lattice parameter [17].…”

Field-induced chirality in the helix structure of Ho/Y multilayers

“…The rare-earth magnetism attracted much attention in the light of the discovery of 3D long range order, which can occur in rare-earth/yttrium superlattice (SL) structures [1][2][3][4][5][6]. Superlattices of Dy/Y and Ho/Y show a helical order in which magnetic moments are aligned in ferromagnetic sheets within each basal plane, but the orientation of these moments changes from one plane to another one, thus forming a spin helix.…”

Experimental determination of magnetic polariton dispersion curves inFeF2

“…This resurgence of interest is based in part on improved growth techniques which have produced high-quality bulk samples, and have allowed fabrication of ultrathin antiferromagnetic films and multilayers. [1][2][3] These structures allow the exploration of properties that are central to the fundamental physics of magnetism-the exchange interaction and magnetic configurations-in systems with truly localized spins, in contrast to studies on metallic ferromagnets. For example, superlattices of FeF 2 /MnF 2 and CoO/NiO demonstrate strong exchange coupling between the two magnetic systems at the interfaces.…”