EPR of LiNaGe4O9:Mn crystal

Abstract

EPR spectra of manganese ions were studied in lithium-sodium tetragermanate LiNaGe4O9 crystal. The observed spectrum was typical for doping ions in tetravalent Mn4+ state (3d 3, S=3/2) and for main orientations of static magnetic field along the crystal axes (T=296 K) consisted of hyperfine sextuplet from electronic transition Ms= +1/2 ↔ – 1/2. Transitions Ms= ±3/2 ↔±1/2 were not detected owing to strong interaction of the spin system with crystal field as compared with electron Zeeman interaction in the X frequency range of EPR registration. The angular variations of the spectrum were measured for static field B rotated in three main crystal planes. Since only central transition (Ms= +1/2 ↔ – 1/2) was detected and the splitting of the fine structure remained unknown, the spectrum was described in the approximation of effective spin Seff=1/2. The parameters of the spin Hamiltonian, including electron Zeeman and hyperfine interactions, were calculated. The magnetic multiplicity of the spectrum (km=2) evidenced that paramagnetic centers occupied the sites with monoclinic C2 point symmetry. Taking into consideration the positional symmetry as well ionic charges and radii of the guest ion and the hosts, it was concluded that paramagnetic Mn4+ centers substituted for Ge4+ within oxygen octahedral complexes in the crystal lattice of LiNaGe4O9.