Journal of Magnetism and Magnetic Materials 272–276 (2004) 2299–2300 Numerical characterization of the magneto-optical polar Kerr effect of a SiO x /FePt/SiO x /Al multilayer on glass substrate Dongwoo Suh*, Yongwoo Park, Hojun Ryu, Yeung Joon Sohn, Mun Cheol Paek Basic Research Laboratory, Applied Devices Department, Electronics and Telecommunications Research Institute, 161 Gajeong-Dong, Yuseong-Gu, Daejeon 305-350, South Korea Abstract Our computational analysis on the magneto-optical (MO) characteristics of the multilayered FePt showed that its Kerr rotation was larger than that of the bare FePt (|y K |o1). In addition, we found that anomalous behavior of Kerr rotation and ellipticity occurs when the FePt layer was between 5 and 10nm thick for the red and blue wavelength showing a great possibility on the application to high-density optical storage arena. Also, we explained an overall calculation procedure of the multilayered MO sturcture based on the theoretical data. r 2004 Elsevier B.V. All rights reserved. PACS: 75.30.Gw; 75.70.Cn; 75.70-I; 78.20.Ls Keywords: Magneto-optical Kerr effect (MOKE); SiO x /FePt/SiO x /Al multilayer 1. Introduction As one of the potential candidates for the advanced magneto-optical (MO) recording materials, FePt has been spotlighted because it shows strong perpendicular magnetic anisotropy (PMA) attributed to the crystal structure of L1 0 type [1]. On the other hand, the MO effect of the multilayered FePt as well as that of the bare FePt is also important for practical purposes. In the present paper, we investigated the polar Kerr character- istics of the FePt superlattice sandwiched between two isotropic protective layers of SiO x on a glass substrate coated with 500-nm-thick Al, one of the conventional reflective layers. 2. Computational details The schematic with the computational parameters of the present multilayered structure is shown Fig. 1, where the FePt layer was assumed to be perpendicularly magnetized to the interface, i.e. y M ¼ 0; showing the polar Kerr state. The dielectric tensor of SiO x , aluminum, glass in Fig. 1 was derived from the complex index of refraction, which is (1.449, 0), (2.75, 8.31), (1.5, 0), respectively. With an assumption that the FePt has the ordered L1 0 structure with no crystalline defect, we took the absorptive parts of the optical conductivity, s 1 xx and s 2 xy ; from the calculation results by Perlov et al. [2]. Using the Kramers–Kronig equations and Eq. (1) which constitutes the conductivity–dielectric relation, we cal- culated the dispersive parts (s 2 xx and s 1 xy ) from the absorptive ones and in turn the dielectric tensor of FePt: % e ¼ d ij þ i 4p % s ij o ; ð1Þ where d ij and o are the Kroneker delta and angular frequency, respectively. Referring to the general proce- dure summarized by Mansuripur [3] and Eq. (2) [4], we computed Kerr rotation (y K ) and Kerr ellipticity (Z K )of the multilayer for the various incident angle and the thickness of the FePt layer: y k þ iZ k ¼ s xy s xx ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 1 þ i 4ps xx o r : ð2Þ ARTICLE IN PRESS *Corresponding author. Tel.: +82-42-860-6235; fax: 82-42- 860-5202. E-mail address: dwsuh@etri.re.kr (D. Suh). 0304-8853/$-see front matter r 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2003.12.934