Electronic structure and magnetization of Fe–Co alloys and multilayers

Abstract

The magnetic properties and electronic structure of bcc Fe-Co alloys and multilayers are investigated with the first-principles molecular cluster discrete variational method. The density of states and the contact interactions are obtained for the central atom of each cluster. Besides the local magnetic moment and the isomer shift the occupancies of 3d, 4s, and 4 p shells are investigated when Co atoms are introduced in the immediate vicinity of iron sites. The calculations indicate a varying magnetic moment for Fe atoms and a constant value for Co atoms which is in agreement with experiments. For the superstructures, our results indicate a strong dependence of the local moment, contact field, and isomer shift for Fe atoms with the thick of iron layers. The internal field increases for thicker Fe layers while the local moment decreases which is also in accordance with experimental predictions.

Magnetism of iron clusters embedded in cobalt

“…It has been pointed out before that Fe is magnetically weak because of an insufficient electron-electron interaction to bandwidth ratio, while in Fe-Co alloys this interaction for the Co atoms could increase the exchange splitting of the Fe 3d bands 33,43 . The local magnetic moments for each subshell of Fe 339 in different environments are depicted in Fig.…”

“…24 -33 Many of the calculations focus on small clusters, but there have been a number of papers that have considered clusters larger than 50 atoms. 26,27,30,31 Recently, Paduani and Krause 33 have studied a variety of Fe-Co alloy and multilayer systems using the first-principles molecular cluster discrete variational method. They model different Fe-Co systems with 15-atom embedded clusters of various compositions.…”

Magnetic study of the Fe–Co–Nb μ and Nbss phases

“…It is worth mentioning that the Co atoms in that site do not contribute to the increase of the magnetic moment of m, in opposition to what it should be expected, such as in the case of alpha Fe-Co, where the magnetic moment of Fe increases with the Co content [1,6,7].…”

Ultra‐small, Uniform, and Single bcc‐Phased FexCo1‐x/Graphitic Shell Nanocrystals for T1Magnetic Resonance Imaging Contrast Agents

“…The single-phased Fe 0.50 Co 0.50 /GC, Fe 0.56 Co 0.44 /GC, and Fe 0.62 Co 0.38 /GC nanocrystals were found to have similar M s values of 193.5-196.3 emu g À1 metal, which is in contrast to the reported composition dependence of M s in bulk FeCo alloy where the highest M s was observed at a composition of Fe 0.65 Co 0.35 . [14] The similar M s values of the single-phased nanocrystals and the lower M s values than that of bulk FeCo can be attributed to the small crystal volume and surface spin-canting effects, which result from the absence of magnetic ordering of the surface spins. [4b] The spin-canting effects of magnetic nanocrystals are also known to have a significant influence on their MR signal-enhancing effects (see below).…”