The Fermi surface of random-metallic alloys and the oscillatory magnetic coupling across alloy spacers

Abstract

Calculated Fermi surfaces of Cu 1−x Ni x binary alloys are used to interpret measurements of the periods of oscillations in the magnetic coupling across Cu 1−x Ni x alloy spacers. The lack of observation of damping of such oscillations is shown to be the consequence of the mean free paths on the Fermi surface being long compared with the oscillation periods. It is argued that oscillatory magnetic coupling is an important new technique for probing the Fermi surfaces of random binary alloys.

Fermi-surface effect on magnetic interlayer coupling

“…The phase is affected by the type of extremal points on the spacer Fermi surface, which may change with concentration. The period changes since the length of the Fermi surface caliper changes as confirmed by Okuno [8] and Bobo [9] for a Co/Cu 1−x Ni x /Co system and investigated theoretically by Lathiotakis [10,11,12]. Finally, the amplitude of the MIC oscillation is influenced by the change in nesting at the Fermi surface.…”

“…∆R = R One could expect that the theory breaks down in case of an alloy spacer but as showed in references [10,13] the effect of an alloy spacer is an additional exponential damping factor to the formula for the MIC so that…”

Influence of alloying on the electron momentum density in the Cu-Ni system

“…Inserting the experimental belly radii of the pure constituents, one arrives for xϭ0.5 at p F (alloy)ϭ0.69 a.u., a value which is identical with that found experimentally by the measurement of ferromagnetic exchange coupling across Cu x Ni 1Ϫx layers. 59,60 ͑Classical techniques like the de Haasvan Alphen effect or magnetoacoustic resonance are not applicable in concentrated alloys due to electron scattering introduced by alloy disorder. 61 ͒ Starting with the EMD for free electrons (p)ϭ⍀/(4 3 )(p F Ϫp), where (p) is the step function, we have calculated the Compton profile difference ⌬J and convoluted it with our p z resolution.…”

Fermi surface callipering of chromium alloys

“…In this Special Issue, Lathiotakis et al [1] present theoretical results obtained from a study of oscillatory magnetic exchange coupling in Fe/Cu-alloy/Fe multilayers and the role of the Fermi surface topology of the non-magnetic spacer layer in determining the period of the oscillatory coupling. The study emphasizes the need for quantitative information on the Fermi surfaces of materials, especially disordered alloys, used in the manufacture of magnetic multilayers.…”