EPR spectroscopy has been used in investigations of the unusual 3+ valence state of zirconium. The EPR spectrum of Zr3+, which was initially observed as a parasitic signal in Fehyphen;doped single crystals of ScPO4, was definitively identified by preparing single crystals of ScPO4doped with isotopically enriched (94.6percnt;)91Zr. Single crystals of LuPO4and YPO4doped with both naturally abundant and isotopically enriched Zr were also grown and investigated. The EPR spectrum of Zr3+could be observed at room temperature in the lsquo;lsquo;ashyphen;grownrsquo;rsquo; single crystals of both ScPO4and LuPO4; and, accordingly, the 3+ state is stable at room temperature in these hosts. The spectrum of Zr3+in the YPO4host could only be observed following a ggr; irradiation at 77 K, and this spectrum decayed rapidly with increasing temperature. Axial spinhyphen;Hamiltonian parameters were determined for Zr3+in all three hosts at a sample temperature of 77 K and at room temperature for the ScPO4and LuPO4hosts. In the case of the latter two hosts, the spinhyphen;Hamiltonian parameters were found to exhibit a small temperature dependence. The observedgvalues were not accounted for by previously published secondhyphen;order expressions indicating that additional coupling mechanisms are operative.
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