Increased room temperature ferromagnetism in Co-doped tetrahedral perovskite niobates

Dilute magnetic semiconductors (DMSs), such as (In, Mn)As and (Ga, Mn)As prototypes, are limited to III–V semiconductors with Curie temperatures (Tc) far from room temperature, thereby hindering their wide application. Here, one kind of DMS based on perovskite niobates is reported. BaMxNb(1-x)O3-δ (M=Fe, Co) powders are prepared by the composite-hydroxide-mediated method. The addition of M elements endows BaMxNb(1-x)O3-δ with local ferromagnetism. The tetragonal BaCoxNb(1-x)O3-δ nanocrystals can be obtained by Co doping, which shows strong saturation magnetization(Msat) of 2.22 emu/g, a remnant magnetization(Mr) of 0.084 emu/g, and a small coercive field(Hc) of 167.02 Oe at room temperature. The ab initio calculations indicate that Co doping could lead to a 64% local spin polarization at the Fermi level(EF) with net spin DOS of 0.89 electrons·eV-1, this result shows the possibility of maintaining strong ferromagnetism at room temperature. In addition, the trade-off effect between the defect band absorption and ferromagnetic properties of BaMxNb(1-x)O3-δ is verified experimentally and theoretically.

Methods
The DFT data was collected from the ab initio calculation results of BaMxNb(1-x)O3-δ, which is performed by CASTEP. M(H) data was collected by the field-dependent magnetization measurement. XRD data was collected by X-ray diffraction. XPS data was collected by X-ray photoelectron spectroscopy. UV data was collected by UV-vis absorption measurement.