Calculation of the electronic structure, lattice dynamics, and optical and magnetic properties of europium tetraborate EuB4O7

Abstract

The electronic band structure, lattice vibration frequencies, and optical and magnetic properties of EuB₄O₇ crystal with α-SrB₄O₇-type structure are calculated within the density functional method. It is found that this compound is a dielectric with a band gap of the order of 4 eV. It is found that the ground state of this crystal is the state with ferromagnetic ordering of Eu²⁺ spins. Exchange interaction constants are calculated; the ferromagnetic ordering temperature is estimated within the molecular field approximation (T_c ≈ 1 K). The EuB₄O₇ compound is a magnetic pyroelectric and, hence, can exhibit magnetoelectric properties. The calculated polarization change during ferromagnetic ordering of this crystal is 3973 μC/m².