Spin-dependent optical response of multiferroic EuO: First-principles DFT calculations

Abstract

Using first-principles density functional calculations, electronic and optical properties of ferromagnetic semiconductor EuO are investigated. In particular, we have developed a way to obtain the spin-dependent optical response of the magnetic materials, which is helpful to verify the spin-dependent band structure of EuO. Significantly different optical responses from spin-up and spin-down channels are obtained in both linear and nonlinear cases, making it possible to distinguish contributions from different spin-channels in the optical absorption spectra if spin-flip process can be neglected. In addition, the red-shift of the absorption edge from paramagnetic to ferromagnetic ordering is explained by exchange interactions. Using such method, we have also compared the optical properties of multiferroic EuO which is induced by strong epitaxial strain. Our results show that from tensile to compressive strain, the blue-shift of the leading absorption peaks in the optical spectra, the red-shift of the optical band gap in spin-up state can be observed, consistent to the energy difference between spin-splitting orbits. The spin-dependent nonlinear optical properties reveal that in the infrared and visible light region, the contributions to second-harmonic generation (SHG) susceptibilities are mainly from spin-majority channels. In addition, the strain effect is also discussed. With the increase of epitaxial strain, the larger energy shift of the leading absorption peaks, and the more remarkable nonlinear optical response can be obtained.

Concepts of ferrovalley material and anomalous valley Hall effect

“…The convergence criterion for the electronic energy is 10 −6  eV and the structures are relaxed until the Hellmann–Feynman forces on each atoms are <1 meV Å −1 . For the optical property calculations, we adopt our own code OPTICPACK that has been successfully applied to study the spin-dependent optical properties in ferromagnetic materials49. The imaginary part of the complex dielectric function ɛ 2 excited by circularly polarized light is calculated using the following relations:…”

Magnetic ordering induced giant optical property change in tetragonal BiFeO3

“…The optical calculations are performed using our own code OPTICPACK, which has been successfully applied to study the optical properties of borate crystals 64 65 and other multiferroic materials 66 . For the linear case, the imaginary part of the complex dielectric function ε 2 is calculated using the following relations:…”

Temperature-dependent lattice dynamics and electronic transitions in0.93Pb(Zn1/3Nb2/3)Zhang1, Tong2, Zhu3 et al. 2015Phys. Rev. BSelf Cite250101View full textAdd to dashboardCite

“…Hence we used different B-site cation arrangements for different phases in order to construct a cluster containing Zn and Nb atoms in the same ratio 1:2 for all the three phases: 1:2 ordering along the [111] c direction for the cubic and rhombohedral phases and 1:2 ordering along the [001] c direction for the tetragonal phase. The results of optical calculations are based on the independent-particle approximation using our own code OPTICPACK [25]. The interband optical conductivity tensor can be written as…”