Paramagnetic Resonance of Mn2+ in Glasses and Compounds of the Lithium Borate System

Abstract

The paramagnetic resonance spectra of Mn²⁺ ions in glasses and compounds of the lithium borate system have been investigated at 9.1 and 35 GHz. The spectrum for the Li₂O·4B₂O₃ compound is found to exhibit six very sharp hyperfine lines centered on g=3.3 when observation is made at X band, while at 35 GHz the center of the principal hyperfine sextet is seen to have shifted to g=2.0. This spectrum is interpreted by assuming a spin Hamiltonian containing crystal‐field terms comparable to the Zeeman energy at X band. By means of a computed diagram it is determined that | D | /h=3.7 GHz and | E/D | =0.333. The same diagram is found useful in interpreting the ESR spectra of Mn²⁺ in lithium borate glasses. It is shown that in the glasses the manganese ions experience wide spreads of crystal fields, giving rise to fine‐structure parameters ranging from near zero to 4 GHz or greater, with an apparent constraint favoring | E/D | ratios of approximately ⅓. It is concluded that many of the Mn²⁺ sites in the glasses are probably distorted versions of the site occupied in the Li₂O·4B₂O₃ compound.