Hyperfine Field and Electronic Structure in Fe/Co and Fe/Ni Multilayer Systems
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MANABU TAKAHASHI, XIAO HU AND YOSHIYUKI KAWAZOE Institute for Materials Research, Tohoku University, Sendai 980-77,Japan
ABSTRACT We investigate hyperfine field (Hhf) distributions and electronic structures in magnetic Fe5 /Cos and Fe5 /Ni 5 multilayer systems using the standard Green function KKR band structure calculation. For the Fe5/Ni5 system the Hhf at the interfacial Fe site is about 10kG smaller than that at the interior Fe site, however, system the Hhf are almost constant in Fe layer for the Fe5/Co5. At the interfacial Ni site the Hh,, is almost twice as large as at the interior Ni site or in bulk fcc Ni. Valence contributions to the hyperfine fields (H,) play important roles for the Hh! distributions. We discuss the relations between core contribution and local spin moment and between valence contribution and total moment within the 1st and 2nd nearest neighbor shells.
INTRODUCTION Magnetic multilayer films have attracted considerable attention from academic and industrial interests, because they show very interesting physical properties that are useful for magneto-optical recording, e.g. giant magneto-resistance, perpendicular anisotropy and interlayer exchange coupling" 2 . Magnetic thin films and multilayers made by molecular beam epitaxy (MBE) method have attracted growing research interests also because metastable crystalline phases can be obtained by this method 9 ,10 . Nuclear magnetic resonance (NMR) or Mbsbauer spectroscopy study is one of the most powerful methods to obtain the information on electronic, magnetic and crystal structures in solids. However, few studies have been made on the details of hyperfine parameters in such magnetic multilayer systems. Recently, it was shown by Bakkaloglu et al. 3 that two kinds of Fe sites associated with higher and lower hyperfine fields exist in Fe/Co multilayers prepared by magnetron sputtering. They concluded that the Fe sites associated with higher fields are located in the interfacial region and those with lower fields in the interior region. On the other hand, Gutierrez et al. 4 have pointed out that in bcc Ni/[Fe(100)] multilayers made by MBE there are two kinds of Fe sites like Co/Fe multilayer; the higher field Fe sites are in the interior Fe layers and the lower ones in the interfacial Fe monolayers. In this paper hyperfine field distributions in both Fe/Co and Fe/Ni multilayers where all atoms are located on the bcc lattice positions are investigated by a first-principle band structure calculation. The influence of lattice relaxations on the hyperfine fields and local spin moment distributions is also checked. In the next section the geometries and methods used in the present study are briefly mentioned. In section 3 the calculated results and discussions are described. The last section is devoted to the summary.
247 Mat. Res. Soc. Symp. Proc. Vol. 382 01995 Materials Research Society
METHOD In the present study, we consider multilayers consisting of five Co or Ni monolayers and five Fe monolayers periodically in order to investigate the hy
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