Growth and magnetic properties of CoxNi1-x and FexNi1-x ultrathin films on Cu(100)
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Abstract
We have grown ultrathin CoxNi1-x and FexNi1-x films on Cu(100) with varying stochiometry x. We find that these alloy films grow in a fee phase on Cu(100). 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(n=x) for samples with different stochiometry. We use this framework in order to determine T-C(n=x) for FexNi1-x alloy films, in particular for concentrations close to 65% Fe content. Bulk Fe65Ni35 shows a collapse of magnetic long-range order and a fcc-to-bce structural transition, which is the so-called Invar effect. In ultrathin Fe65Ni35 films, we observe a ''quenching'' of the Invar effect, because growth on a Cu(100) substrate forces the film to adept the Cu lattice spacing thereby suppressing the structural relaxation.