We have prepared CoxNi1−x/Pt multilayers by evaporation under ultrahigh vacuum conditions and studied their magnetic and magneto-optical properties. The addition of Co to Ni leads to an increase in both the surface anisotropy and TC. It is found that the surface anisotropy Ks of CoxNi1−x/Pt multilayers can be expressed as the sum of Ks of Ni/Pt and of Co/Pt times their respective concentration. In Co0.3Ni0.7/Pt multilayers, for t(Co,Ni)=0.45 nm, one observes a perpendicular M-H loop with a good rectangularity and a coercivity of 1 kOe and TC of 180 °C. These characteristics are very interesting for application in magneto-optic storage.
Co1−xCux composite films with 0≤x≤83 have been sputter deposited on to water-cooled glass substrates. Transmission electron microscopy and scanning tunneling microscopy studies reveal clusters whose average size is 250 Å. Magnetization when corrected to the Co volume is independent of Cu concentration and is equal to that of bulk Co. The in-plane saturation field is about 200 Oe at x=0, starts increasing for x=40, and shows a peak value of 1.2 kOe for x=60. Coercivity shows a similar behavior. Out-of-plane perpendicular anisotropy develops with the increase in Cu concentration. The ferromagnetic resonance studies show that (i) the linewidth increases for x≳75 and (ii) perpendicular anisotropy, probably induced by stress, also increases with x. Annealing up to 300 °C does not produce any noticeable changes but when annealed at 400 °C the perpendicular anisotropy decreases indicating some stress relief.
Magnetization at 5 K and polar Kerr spectra in CoxNi1-x/Pt multilayers were studied as functions of Co content in
order to better understand the difference in the behaviour of interfacial Co
and Ni atoms. While the magneto-optic enhancement in the Kerr spectra is
observed for the whole range of 00.3 indicating
that Pt atoms are not polarized by the Ni atoms. The x-ray photoelectron
spectroscopy experiments indicate that there is charge transfer from Pt to 3d
bands of Ni at the interface, leading to the loss of ferromagnetism in Ni.
Therefore, non-magnetic Ni is not able to polarize Pt and induce a moment. In
contrast, in the case of Co, no charge transfer is seen and Co remains
ferromagnetic and induces a moment on Pt by polarization effects.
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