HIGH-RESOLUTION SPECTROSCOPY AND OPTICALLY DETECTED NUCLEAR-MAGNETIC-RESONANCE STUDIES OF HO3+ IONS IN SRF2 CRYSTALS CONTAINING BA2+ AND CA2+ IMPURITIES
M. Mujaji et al., HIGH-RESOLUTION SPECTROSCOPY AND OPTICALLY DETECTED NUCLEAR-MAGNETIC-RESONANCE STUDIES OF HO3+ IONS IN SRF2 CRYSTALS CONTAINING BA2+ AND CA2+ IMPURITIES, Journal of physics. Condensed matter, 5(23), 1993, pp. 3937-3944
Optical-RF double-resonance techniques have been used to measure the s
uperhyperfine transition frequencies of two Ho3+ centres of C4v symmet
ry present in SrF2:0.001%Ho3+ crystals containing about 0.2% of Ba2+ a
nd Ca2+ as inadvertent impurities, One centre has a charge-compensatin
g F- ion located in the nearest-neighbour interstitial position along
the (100) axis while the other has an additional Ba2+ ion also located
on this axis. The superhyperfine transition frequencies are about 60%
smaller than those reported for CaF2:Ho3+ and these decreases are att
ributed principally to the decreased Ho3+ ground-state magnetic moment
resulting from the increased energy separation between the ground and
first excited state Ho3+ electronic energy levels. Another contributi
on arises from the larger host lattice dimension for SrF2. The two set
s of nearest-neighbour F- ions have almost identical resonance frequen
cies for both SrF2 centres while the interstitial F- ion has a substan
tially reduced resonance frequency in the Ba2+ modified centre. These
trends correlate with those in the relevant crystal-field parameters.
Some qualitative conclusions are drawn about the positions of the Ho3 and F- ions in these centres.