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Exchange coupling between two magnetic layers in a quasi‐one‐dimensional potential well
Author(s) -
Wang Zhongcheng,
Wang Shaofeng,
Hou Weihong
Publication year - 1996
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221970128
Subject(s) - condensed matter physics , coupling (piping) , physics , electron , effective mass (spring–mass system) , ferromagnetism , rkky interaction , exchange interaction , fermi surface , function (biology) , magnetic moment , spin (aerodynamics) , anisotropy , quantum mechanics , materials science , thermodynamics , evolutionary biology , metallurgy , biology
Exchange coupling between two magnetic monolayers mediated by electrons confined in a quasi‐one‐dimensional potential well is investigated. By using a Green's‐function method and approximate expansion, an analytic expression is derived for the weak coupling within the contact interaction approximation. As a main result of the quantum size effect, the number of occupied levels and the Fermi energy are found to be periodic functions of the sample thickness. If the anisotropy in the effective electron mass is taken into consideration, the period is given by \documentclass{article}\pagestyle{empty}\begin{document}$ T = \sqrt[3]{{{{\pi \mu _\parallel } \mathord{\left/ {\vphantom {{\pi \mu _\parallel } {\left({6n_0 \mu _ \bot } \right)}}} \right. \kern-\nulldelimiterspace} {\left({6n_0 \mu _ \bot } \right)}}}} $\end{document} , where μ| and μ⊥ are the effective electron mass in the surface and growth direction, respectively, and n 0 is the electron density for one spin. Because of the quantum size effect, the exchange coupling cannot be considered as a simple oscillatory function of the distance between the two magnetic layers. It depends on the distance between the two magnetic layers as well as on the distance from the magnetic layer to the sample surface. For some distance from the magnetic layer to the sample surface, the exchange coupling with the distance between two magnetic layers shows a similar analytic behaviour as the RKKY interaction does. However, for some other distance, there may be just a strength oscillation of the ferromagnetic coupling.