Electron paramagnetic resonance (EPR) investigations of the local environment around Co2+ ions doped in PbMoO4 single crystals – Correlation with optical studies

Spin Hamiltonian Parameters for Co2+Ions in PbMoO4Crystal - Interplay between the Fictitious Spin S'=1/2 and the Effective Spin S̃ =3/2

“…The results [19] correlate well with interpretations of earlier optical measurements [22], thus suggesting that Co 2+ ions substitute at the Mo 6+ tetrahedral sites. The g i values [19] are very close to the principal g i values determined for Co 2+ in PbWO 4 crystals by Chen and Artman [17,18]. Correlation between the experimental (or calculated) principal g-tensor values: g i for the S = 1/2 ground Kramers doublet and g i for theS = 3/2 multiplet, may be achieved using the relations given in [17]:…”

“…Concerning the orientation of the principal axes of the g-tensor for the complexes Co 2+ (α) with respect to the crystallographic axes (a, b, c) in PbMoO 4 crystal, we follow the definitions outlined in [19,22]. The results [19] correlate well with interpretations of earlier optical measurements [22], thus suggesting that Co 2+ ions substitute at the Mo 6+ tetrahedral sites. The g i values [19] are very close to the principal g i values determined for Co 2+ in PbWO 4 crystals by Chen and Artman [17,18].…”

“…The secondrank ZFSPs D and E and the Ze g i factors are indirectly determined for the effective spinS = 3/2 from available experimental EMR data on the Ze g i factors established for the fictitious "spin" S = 1/2 [17][18][19]. For this purpose, we employ the formulae [17] arising from projection of the g i (S = 3/2) factors onto the g i (S = 1/2) factors.…”

“…Analysis of EPR data [19] has revealed that Co 2+ ions doped into PbMoO 4 may be characterized by the fictitious spin S = 1/2 with the Ze g i factors listed in Table I. Concerning the orientation of the principal axes of the g-tensor for the complexes Co 2+ (α) with respect to the crystallographic axes (a, b, c) in PbMoO 4 crystal, we follow the definitions outlined in [19,22].…”

Origin of the Ground Kramers Doublets for Co2+(3d7) Ions with the Effective Spin 3/2 Versus the Fictitious ‘Spin’ ½

“…This offers potential applications ranging from the Co 2+ compounds, which may be suitable as high-pressure probes for high-magnetic field and high-frequency EMR (HFM-EMR) measurements [5][6][7], to Co 2+ -based molecular nanomagnets exhibiting very large or moderate ZFS, including single-molecule magnets (SMM) and single-ion magnets (SIM) [8]. As a case study, we investigate: (1) the polarized optical absorption and EMR spectra of Co-doped beryls and chrysoberyl [9], (2) EMR spectra of Co 2+ (S′ = ½) ions in PbMoO 4 and YAlO 3 [10,11]. The calculations are carried out using the crystal field analysis (CFA) package [12], which enables the complete diagonalization within the whole 3d N configuration for arbitrary symmetry.…”