C. B. Finch

EPR Investigations of Er3+, Yb3+, and Gd3+ in Zircon‐Structure Silicates

The EPR spectra of Er3+, Yb3+, and Gd3+ have been observed in the host single crystals ZrSiO4, HfSiO4, and ThSiO4 which were grown by a flux‐gradient technique. For most systems, spectra were observed which exhibited both tetragonal and orthorhombic symmetry. The tetragonal spectra were characterized by a principal axis system which coincided with the principal crystallographic axes. The observed orthorhombic spectra were of two types. For Gd3+ in ZrSiO4 and HfSiO4, orthorhombic spectra due to eight inequivalent sites were observed and had principal axis systems which were not simply related to the host crystallographic axes. All other orthorhombic spectra resulted from four inequivalent sites whose z and x axes lay in {110} planes with equal angles between the crystal tetragonal symmetry axis (c axis) and each z axis. For both types of orthorhombic spectra, the corresponding EPR transitions from the different sites were super‐imposed with the applied magnetic field parallel to the c axis. Spin‐Hamiltonia...

Ground‐State Splitting of Trivalent Gd and Cm in ZrSiO4, HfSiO4, and ThSiO4, Determined by ESR

The electron spin resonance spectrum of trivalent gadolinium impurity in the tetragonal host crystals of ZrSiO4, ThSiO4, and HfSiO4 has been observed at X band, and the spin‐Hamiltonian parameters were obtained at various temperatures. The dominant second‐order parameter B20 for Gd was observed to be negative in all three crystals. Hyperfine structure for the odd isotopes 155Gd and 157Gd was clearly resolved and measured. In ThSiO4 crystals doped with trivalent curium, no ESR signals were detected, supporting the assumption of a large negative B20 term for this ion in these hosts.

Paramagnetic resonance of Gd3+ in CeO2 single crystals

Abstract Gd 3+ has been incorporated into single crystals of CeO 2 (fluorite structure) in cubic sites and the ESR spectrum observed. The temperature dependence of the cubic crystal splitting has been measured from room temperature to ≈ 2°K and values of g , the fourth order parameter, c , and the sixth order parameter, d , in the spin Hamiltonian treatment for the crystal field potential have been obtained using a computer program. The parameters c and d were found to have the same sign and intensity observations of the temperature dependence of the resonance absorption lines showed that c was negative. The temperature dependence of the total splitting for H ∥[100] was found to be similar to that observed in Gd 3+ : ThO 2 . Forbidden transitions with ¦ Δ M 5 ¦ #62; 1 were observed, as well as axial spectra in heavily doped crystals. Lines due to transitions with Δ M 5 = ± 4 were identified in both ThO 2 and CeO 2 .

EPR determination of the nuclear spins and magnetic moments of 243Cm and 247Cm

Abstract EPR spectroscopy has been employed in making the first direct measurements of the nuclear spins of 243 Cm and 247 Cm ( I = 5 2 and I = 9 2 respectively). Estimated nuclear moments are |0.4μ N | for 243 Cm and |0.36 μ N | for 247 Cm.

Electron paramagnetic resonance of 249Bk4+ in ThO2 single crystals

Abstract The EPR spectrum of Bk 4+ has been obtained for the first time. For a ThO 2 host, a Γ 6 doublet lies lowest. The nuclear spin of 249 Bk is confirmed as 7 2 and the estimated nuclear moment is 2.2 μ N .

Zero‐Field Splittings of Cm3+ and Am2+ in Fluorite Type Crystals

The Γ6—Γ8 energy level splittings were derived for Cm3+ and Am2+ in several fluorite type crystals from measurements of the anisotropy of the g value of the Γ6 state at 35 GHz. Anisotropy measurements were also made of the g value of the excited Γ7 state for Cm3+ in SrCl2, and the Γ8—Γ7 splitting was obtained.

Electron paramagnetic resonance of 239Pu3+ and 243Am4+ in CeO2 and of 241Pu3+ in ThO2

The g values of the 5f5 ions Pu3+ and Am4+ in CeO2 cubic symmetry sites have been measured by EPR techniques and found to be 1.333 ± 0.001 and 1.3120 ± 0.0005, respectively. For the case of Pu3+, the cubic crystal field parameters were calculated and compared with those previously obtained for other fluorite‐structure lattices. The EPR spectrum was also observed for 241Pu in ThO2 and the ratio of the magnetic moments 241μI/239μI determined to be 3.52 ± 0.06.

Promethium‐doped phosphate glass laser at 933 and 1098 nm

A promethium (Pm3+) laser has been demonstrated for the first time. Trivalent promethium 147 doped into a lead‐indium‐phosphate glass etalon was used to produce room‐temperature four‐level laser emission at wavelengths of 933 and 1098 nm. Spectroscopic and kinetic measurements have shown that Pm3+ is similar to Nd3+ as a laser active ion.

Growth of monoclinic macrocrystalline ZrO2 by hydrolysis of ZrF4-LiF-NaF melts at 650–800°C

Abstract Macrocrystalline monoclinic ZrO2 crystals up to 3 mm size were grown during hydrolysis of LiF-NaF-ZrF4 melts at 650–800°C.

Edge-defined, film-fed growth of Mn2SiO4-MnO eutectic composites: Effect of die-top geometry on solidification interface shape

The effect of die-top geometry (planar, convex, or concave) on solidification interface shape was investigated during edge-defined, film-fed growth (EFG) of Mn2SiO4-MnO eutectic composites. The composites were solidified as a function of growth rate (3 to 30 mm/h) from melts of the initial compositions Mn2SiO4-15 and -29 mole% MnO. Banding effects attest that the solidification interfaces have contours which approach the die-top geometries used. An aligned microstructure of <1 μm diameter MnO rods in an Mn2SiO4 matrix was obtained at growth rates of <15 mm/h. Discontinuities in rod growth at 1 to 5 μm intervals suggest mock lateral growth of the matrix. Independent of die-top geometry, an unbanded cellular microstructure predominated in boules grown at 20 mm/h or more.