Magnetic properties of (111) oriented Ni1−xFex alloy thin films (abstract)

Abstract

We present a study of changes in the magnetic properties of 4 ML face-centered-cubic (fcc) Ni1−xFex(111) thin films as a function of Fe concentration. These Ni1−xFex films were grown epitaxially on Cu(111)substrates using codeposition of Ni and enriched Fe57. The use of Cu substrates offers the ability to stabilize the fcc phase across the entire Fe concentration range making a study of the fcc phase at high Fe concentrations possible. The magnetic properties were studied by utilizing a combination of Mössbauer spectroscopy and SQUID magnetometry to gain a more complete picture of the magnetic order. For low Fe concentrations the Mössbauer data displayed only a high-spin ferromagnetic (FM) phase. However, as the Fe concentration was increased, the Mössbauer spectra showed the clear appearance of a low-spin antiferromagnetic (AFM) phase coexisting with the FM phase. Magnetometry observed the appearance of this state as a drop in the average saturation moment above x=0.65. Such a transition is in agreement with our finding that the pure Fe film is described by a coexisting FM and AFM order. Also observed where changes in the perpendicular anisotropy. The anisotropy shows changes towards favoring a perpendicular easy axis, but the system appears to have an in-plane easy axis for all concentrations.