In order to investigate the mechanism of ferromagnetic ordering in the new n-type magnetic semiconductor (In,Fe)As co-doped with Be, we have performed X-ray absorption spectroscopy and X-ray magnetic circular dichroism (XMCD) studies of ferromagnetic and paramagnetic samples. The spectral line shapes suggest that the ferromagnetism is intrinsic originating from Fe atoms incorporated into the Zinc-blende-type InAs lattice. The magnetization curves of Fe measured by XMCD were well reproduced by the superposition of a Langevin function representing superparamagnetic (SPM) behavior of nano-scale ferromagnetic domains and a T-linear function representing Curie-Weiss paramagnetism even much above the Curie temperatures. The data at 20 K showed a deviation from the Langevin behavior, suggesting a gradual establishment of macroscopic ferromagnetism on lowering temperature. The existence of nano-scale ferromagnetic domains indicated by the SPM behavior suggests spatial fluctuations of Fe concentration on the nano-scale.
@article{arxiv.1505.01402,
title = {Magnetization Process of the n-type Ferromagnetic Semiconductor (In,Fe)As:Be Studied by X-ray Magnetic Circular Dichroism},
author = {Shoya Sakamoto and Le Duc Anh and Pham Nam Hai and Goro Shibata and Yukiharu Takeda and Masaki Kobayashi and Yukio Takahashi and Tsuneharu Koide and Masaaki Tanaka and Atsushi Fujimori},
journal= {arXiv preprint arXiv:1505.01402},
year = {2016}
}