X-ray magnetic-circular-dichroism study of Ni Fe (001) multilayers

The structure and magnetic properties of Fe/Ni(001) multilayers are studied using x-ray diffraction, magneto-optical Ken effect magnetometry, and x-ray magnetic circular dichroism. Multilayers are deposited with constant Fe layers (12 Angstrom) and wedged Ni layers (0-30 Angstrom), repeated 20 times, to explore the magnetic moment and the structure dependence upon thickness of Ni (t(Ni)). Up to t(Ni)approximate to 16 Angstrom (11 ML), both the Fe and the Ni have a bet structure, similar to the bulk structure of bcc Fe. The magnetic moments of Ni in the bet region are nearly constant at 0.85 mu(B) for a Ni thickness t(Ni) in the range 3 Angstrom < t(Ni) < 16 Angstrom. This represents a significant enhancement over the moment in bulk fee Ni (0.59 mu B). The Fe/Ni multilayer undergoes a crystalline phase transition between 16 Angstrom < t(Ni) < 23 Angstrom, beyond which both the Fe and Ni have an fct structure. In the fct region, the Ni magnetic moment is close to its bulk value and the Fe magnetic moment drops to 1.5 mu(B),, which is similar to 70% of its bulk value. The crystalline phase transition is also accompanied by a rotation of the magnetic easy axis by 45 degrees in the plane of the film. [S0163-1829(99)13521-5].