ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Recently, magnetic properties of fcc-Fe ultrathin films have been extensively investigated. The results, however, are complicated and inconsistent with one another. These are antiferromagnetism, ferromagnetism, different Fe magnetic moment for different atomic sites in film or a rearrangement of surface Fe atoms etc. In this article the recent results for fcc-Fe multilayers will be reported and discussed to obtain a unified picture for magnetism of fcc-Fe ultrathin films. Epitaxially grown multilayers of fcc-Fe with Cu or Cu-M (M=Au,Ni) spacer on Cu(001) and Cu(111) substrates were prepared by molecular beam epitaxy method. The Cu-M spacer was adopted to change the mean interatomic distance between Fe atoms at interfaces by changing the composition of M (=Au,Ni), where Au was used to increase the distance and Ni to decrease it. Fe layers on a pure Cu spacer were fcc and the magnetic moment was at most 2.0μB. Fe layers on a Cu-Au spacer, however, were fct with c/a〈1 and those on Cu-Ni with c/a(approximately-greater-than)1, where a is the in-plane lattice constant and c is the out of plane one. Then a mean magnetic moment of Fe atoms (μ) as a function of Fe atomic volume (V) was obtained. The moment μ continuously increases with increasing V by the so-called magnetovolume effect. The maximum μ value is 2.7μB for about ΔV=4% (ΔV is a change of V from pure Cu volume). And μ=0 for ΔV=−2%. The Mössbauer effect and EXAFS were also measured.The measurements revealed that the samples for the ΔV≤0 region contain two kinds of Fe (mixture state), high spin state with 2.0μB and nonmagnetic low spin state. Thus it is concluded that the high to low spin state transition is the first kind as theoretically suggested by Moruzzi et al. We also performed band calculations for fcc-Fe/Cu multilayers changing V. Next, the reason for the mixture state is discussed. It is found that a well defined smooth Cu substrate surface promotes a rearrangment of surface Fe atoms due to the surface diffusion, preferring the low spin state and the rough surface obstructs the rearrangement and provides the fcc circumstance by surrounding Cu atoms, which results in the high spin state. Recent inconsistent results for fcc-Fe ultra thin films could be explained by the two spin state model, the surface Fe atomic rearrangement, and the magnetovolume effect. © 1996 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.362248
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