EPR study of Mn²⁺ doped nanocrystalline PbF₂

Abstract

Nanocrystalline samples of PbF₂ doped with 0.05, 0.1, 0.4 and 1 mol% Mn²⁺, used as paramagnetic probe, were prepared by inert gas condensation technique. All the samples were vacuum annealed at different temperatures to get different grain sizes. The X-ray diffraction studies showed the dominant content of β-PbF₂ phase with a fractional quantity of α-PbF₂. Thermal stability and sublattice melting were studied by TGA and DSC respectively. EPR measurements were made on all these samples at 77 and 300 K. The EPR spectra of all samples were found to contain well resolved sextet arising from the Mn²⁺ ions that occupied the cubic sites of Pb²⁺ ion of PbF2 lattice. The lower concentration of the Mn²⁺ ions (0.05 and 0.1 mol%) clearly monitored the Pb²⁺ environment in the PbF₂ lattice. The 0.4 mol% showed the presence of only the cubic sites with a minor concentration of the orthorhombic sites. The spectra corresponding to 1 mol% Mn2+ clearly showed two different components. The isotropic nature of the 1 mol% as-prepared sample implied that there was no cluster formation and hence this EPR spectrum was taken as the single ion spectrum. The annealed samples contain two spectral components; one is from the isolated single ions and the other one from the Mn²⁺ clusters. The spectral component of Mn²⁺ clusters was obtained by subtracting the spectrum for the as-prepared sample for the spectra of annealed samples. The extracted cluster phase spectra and the pure spectrum from the as-prepared sample were then combined to simulate the entire set of experimental spectra. The simulated spectra were found to be in good agreement with the experimental data. The g values obtained were in the range very close to the free electron g factor as the electrons are in the S state (L=0).