Characterization of Electronic Properties, Exchange Splitting and Ferromagnetic Arrangement in New Ti-Doped BaO

We have studied the electronic structures, ferromagnetic properties, half-metallicity and exchange splitting in BaO doped with titanium such as Ba1-xTixO at concentration x = 0.125. The structural parameters of BaO and Ba0.875Ti0.125O compounds are calculated with generalised gradient approximation of Wu and Cohen, while their electronic structures, accurate band gaps and magnetic properties are evaluated by the use of the Tran-Blaha-modified Becke-Johnson potential. The changes of lattice parameter and bulk modulus of Ba0.875Ti0.125O are discussed with respect to the BaO. We have found that the Ba0.875Ti0.125O has a wide half-metallic ferromagnetic gap of 2.701 eV and a half-metallic gap of 0.803 eV with integral Bohr magneton of 2 μB, where its ferromagnetic state is characterised by the main contribution of the direct exchange splitting. Therefore, the Ba0.875Ti0.125O is true half-metallic ferromagnet with spin polarisation of 100 % and appears to be promising material for spintronics applications.

Topological magneto-optical effects and their quantization in noncoplanar antiferromagnets

Reflecting the fundamental interactions of polarized light with magnetic matter, magneto-optical effects are well known since more than a century. The emergence of these phenomena is commonly attributed to the interplay between exchange splitting and spin-orbit coupling in the electronic structure of magnets. Using theoretical arguments, we demonstrate that topological magneto-optical effects can arise in noncoplanar antiferromagnets due to the finite scalar spin chirality, without any reference to exchange splitting or spin-orbit coupling. We propose spectral integrals of certain magneto-optical quantities that uncover the unique topological nature of the discovered effect. We also find that the Kerr and Faraday rotation angles can be quantized in insulating topological antiferromagnets in the low-frequency limit, owing to nontrivial global properties that manifest in quantum topological magneto-optical effects. Although the predicted topological and quantum topological magneto-optical effects are fundamentally distinct from conventional light-matter interactions, they can be measured by readily available experimental techniques.