Synthesis and Optical Properties of Nickel-Doped Copper Metaborate Crystals

This work presents information on the growth and spectroscopic study of single crystals of copper metaborate doped with nickel Cu1-xNixB2O4 (x= 0.05, 0.1). In the absorption spectra of both crystals, satellites related to Cu centers distorted by impurity Ni atoms were observed near the lines of zero phonon transitions. Polarization studies in the isotropic ab-plane of the tetragonal crystal Cu1-xNixB2O4 show the presence of linear magnetic dichroism in the magnetically ordered state, which was previously observed both in manganese-doped and undoped copper metaborates CuB2O4. The temperature of magnetic phase transitions into the collinear antiferromagnetic and into helicoidal structures, T-N= 19.1 K and T * = 8.6 K, respectively, were determined from the temperature dependence of the dichroic signal.