Magneto-optical spectra of Fe/Au artificial superlattices modulated by integer and non-integer atomic layers

Katsuaki Sato , Eishi Takeda and Masanori Akita,
Faculty of Technology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan,

Masatake Yamaguchi
Center for Promotion of Computational Science and Engineering, Japan Atomic Energy Research Institute, Tokai-mura, Ibaraki 319-1195, Japan

Koki Takanashi, Seiji Mitani and Hiroyasu Fujimori,
Institute for Materials Research, Tohoku University, Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan,

Yoshishige Suzuki,
Joint Research Center for Atom Technology, Tsukuba, Ibaraki 305-8562, Japan

Abstract - Spectra of the magneto-optical Kerr effect, in a series of [Fe (xML)/Au(xML)]N superlattices with integer and non-integer values of x (1 smaller than or equal to x smaller than or equal to 15), were measured. For x=1 the superlattice forms an L10-type ordered alloy structure. The magneto-optical spectrum of the superlattice exhibits a prominent structure around 4 eV, which shows a systematic shift toward higher energies as x increases (1 smaller than or equal to x smaller than or equal to 5). No such structure can be reproduced by an optical calculation assuming a simple stack of thin Fe and Au layers. Ab-initio band calculations have shown similar magneto-optical spectra and a similar peak shift with an increase in x (1 smaller than or equal to x smaller than or equal to 6). This suggests that electronic structures which differ from that of a simple stack of thin Fe and Au are realized in the superlattices. For non-integer values of x, an oscillatory behavior with a period of one monolayer was observed in the low energy region of the magneto-optical spectra.

KEYWORDS: Fe/Au superlattice, magneto-optical effect, spectrum, quantum well, ordered alloy