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 M_s= +1/2 ↔ – 1/2. Transitions M_s= ±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 (M_s= +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 S_eff=1/2. The parameters of the spin Hamiltonian, including electron Zeeman and hyperfine interactions, were calculated. The magnetic multiplicity of the spectrum (k_m=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.