Growth and magnetic properties ofCoxNi1−xand

F. O. Schumann

¹

,

Shan Wu

²

,

G. J. Mankey

³

et al.

Abstract

We have grown ultrathin Co x Ni 1Ϫx and Fe x Ni 1Ϫx films on Cu͑100͒ with varying stochiometry x. We find that these alloy films grow in a fcc phase on Cu͑100͒. With the surface magneto-optic Kerr effect we measured the variation of the Curie temperature T C as a function of the film thickness n in monolayers. Fitting an empirical scaling curve to our results we are able to extrapolate the value T C (nϭϱ) for samples with different stochiometry. We use this framework in order to determine T C (nϭϱ) for Fe x Ni 1Ϫx alloy films, in particular for concentrations close to 65% Fe content. Bulk Fe 65 Ni 35 shows a collapse of magnetic long-range order and a fcc-to-bcc structural transition, which is the so-called Invar effect. In ultrathin Fe 65 Ni 35 films, we observe a ''quenching'' of the Invar effect, because growth on a Cu͑100͒ substrate forces the film to adopt the Cu lattice spacing thereby suppressing the structural relaxation.

Magnetic properties of Fe-based alloys

“…[4][5][6][7][8] The focus of this work is Fe-based alloys, which can be prepared in a fcc phase throughout the whole concentration regime. 9,10 This contrasts the behavior of the bulk, where a bcc phase is adopted for Fe-rich alloys. In this work we will use magnetic linear dichroism in angleresolved photoemission with linear polarized light ͑MLDAD͒.…”

Relation of domain properties to structural changes in perpendicularly magnetized ultrathin films

“…The quadratic dispersion constant of spin waves at small wave vector 41 (ϳ2JS) and the magnetic moments (ϳg s B S) were used to calculate J Ni,Ni ͉S Ni ͉ 2 ϭ51 K and J Fe,Fe ͉S Fe ͉ 2 ϭ218 K. An approximate value for J Ni,Fe S Ni •S Fe is found by scaling J Ni,Ni ͉S Ni ͉ 2 by the ratio of T c for ultrathin equal concentration FeNi alloy films and Ni films. 42 For layered and mixed films, an average exchange can be defined as…”

Photoemission study of Fermi surfaces of pseudomorphic Co, Ni, andCoxNi1−xfilms on Cu(100)

“…14,15 This allowed us to investigate the electronic properties of these alloys with changing composition independent of any change in their lattice structure. All films were grown to a thickness of 8 ML to avoid any contribution from the electronic structure of the Cu substrate.…”

“…12,13 It has been demonstrated that it is possible to grow ultrathin fcc Co 1Ϫx Ni x alloy films epitaxially on Cu͑100͒ with variable stoichiometry. 14,15 For Co 1Ϫx Ni x alloy films, the fcc phase is adopted in the whole concentration range and the magnetic moment varies linearly between the values of Ni and Co, while the Curie temperature remains a monotonic function of the composition. The lattice of pseudomorphic fcc Co x Ni 1Ϫx alloy films remains constant throughout the whole concentration range.…”