Paramagnetic resonance of Mn²⁺ in KNO₃ single crystal: motional effects

Abstract

The electron paramagnetic resonance of Mn²⁺ in KNO₃ single crystal is investigated over a temperature cycle through transition temperatures. The hyperfine coupling constant, A, half width,Δ H, and the line intensity, I, are found to show sudden changes at the transition temperature, at which α-KNO₃ changes into β -KNO₃. The lines are much sharper in the high temperature β -phase than in α -phase of the crystal. They are explained, qualitatively, in terms of structure change and rotation of NO₃₋ ions. The spectra in the two phases,α andβ , are analysed in terms of usual spin-Hamiltonian. A search of metastable γ -phase is also made and probable indications for the same are found.