Origin of perpendicular magnetic anisotropy and evolution of magnetic domain structure of amorphous Pr–TM–B (TM=Fe, Co) films W.Y. Zhang a,n , H. Shima a , F. Takano a , M. Takenaka a , M. Yamazaki a , K. Masuda a , H. Akinaga a , T. Nagahama b , S. Nimori c a Nanodevice Innovation Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan b NanoElectronics Research Institute, AIST, Tsukuba Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan c Tsukuba Magnet Laboratory, National Institute for Materials Science, 3-13 Sakura, Tsukuba, Ibaraki 305-0003, Japan article info Article history: Received 15 September 2009 Available online 24 November 2009 Keywords: Magnetic force microscopy Magnetic thin films Perpendicular magnetic anisotropy Residual stress abstract In this study, the deposition pressure dependence of the compositional ratio, magnetic domain structure, and perpendicular magnetic anisotropy (PMA) of B-containing PrFe- and PrCo-based films, which are rare-earth–transition-metal (RE–TM) films, was investigated. PrFe- and PrCo-based films were fabricated by magnetron sputtering. The film compositions were controlled in a wide range by varying the deposition pressure. On the basis of experimental results, the residual stress of the films was considered to be the possible origin of their PMA. The films showed strong magneto-optical effects over the entire wavelength range of 300–750 nm. Because of the excellent magnetic and magneto- optical (MO) properties of the films, they have high potential for MO applications at wavelengths of red and blue lasers. & 2009 Elsevier B.V. All rights reserved. 1. Introduction Perpendicular magnetic anisotropy (PMA) of amorphous rare-earth–transition-metal (RE–TM) films showing a strong magneto-optical (MO) Kerr effect has attracted significant attention due to its importance for the transverse-magnetic- mode waveguide isolator and magneto-optical (MO) applica- tion [1–3]. It is known that strong PMA is an indispensable factor for achieving good magnetic properties of RE–TM films, which is a requirement for their use in MO applications. A considerable number of studies have been conducted for exploring the origin of PMA in TbFe-based films, in order to enhance it further. So far, several physical mechanisms, such as the chemical short-range order, single-ion anisotropy, presence of local clusters, and bond-orientational anisotropy have been studied for explaining the origin of PMA of TbFe-based films [4–7]. Compared to an amorphous TbFe-based film, an amor- phous (Nd,Pr)–(Fe,Co) film showing PMA may have a wider range of MO applications, due to its considerably larger Kerr rotation angle at the wavelength of the blue laser and much richer source of rare-earth elements in the earth’s crust [8,9]. However, few studies have been conducted for elucidating the origin of PMA of amorphous (Nd,Pr) (Fe,Co) films. RE–TM films are required to have a single amorphous phase for their practical application [10]. It is known that the preparation of the single amorphous phase Nd–Fe film with high RE content is difficult because of phase separation induced by the positive mixing heat of Nd and Fe [11,12]. Therefore, in a previous study, an amorphous Pr(Fe,Co) film with low RE content was selected as the subject of research. In that study, it was found that an amorphous NdFe film with low RE content did not normally show PMA, because of the large demagnetizing energy induced by high saturation magnetization [13]. In another study, it was found that the addition of nonmagnetic boron to an amorphous NdFe film caused a reduction in the demagnetizing energy of the film, thereby inducing PMA [14]. In addition, it was shown that the large negative mixing heat of Fe–B and Nd–B contributed to the formation of a long-range homogeneous atomic configuration of amorphous Nd–Fe alloys [15,16]. Further, the addition of boron to Pr(Fe,Co) films was expected to greatly improve the possibility of generating single amor- phous phases of Pr(Fe,Co)B films. In this study, the abovementioned results were used to fabricate Pr(Fe,Co)B films showing PMA. Amorphous B-con- taining PrFe- and PrCo-based films showing PMA were fabricated by magnetron sputtering. The Pr contents of the amorphous PrFe- and PrCo-based films were decreased ARTICLE IN PRESS Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jmmm Journal of Magnetism and Magnetic Materials 0304-8853/$ - see front matter & 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2009.11.022 n Corresponding author. Tel.: + 81 29 861 5080x55531; fax: + 81 29 861 3211. E-mail addresses: wenyong.zhang@aist.go.jp, wyzhang2005@yahoo.com (W.Y. Zhang). Journal of Magnetism and Magnetic Materials 322 (2010) 900–908