Magnetization Process of the n-type Ferromagnetic Semiconductor (In,Fe)As:Be Studied by X-ray Magnetic Circular Dichroism

TL;DR

This study investigates the ferromagnetic mechanism in the n-type semiconductor (In,Fe)As:Be using X-ray spectroscopy, revealing intrinsic Fe-based ferromagnetism and nano-scale magnetic domains that influence its magnetic properties.

Contribution

It provides direct spectroscopic evidence that ferromagnetism in (In,Fe)As:Be is intrinsic and originates from Fe atoms in the lattice, and characterizes nano-scale ferromagnetic domains.

Findings

Ferromagnetism is intrinsic and from Fe atoms in the lattice.

Nano-scale ferromagnetic domains exhibit superparamagnetic behavior.

Temperature influences the development of macroscopic ferromagnetism.

Abstract

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.