Electron-nuclear double-resonance investigations on Cr3+ ions in natural MgAl2O4 spinel

The ENDOR spectra of Cr3+ ions in natural MgAl2O4 spinel have been measured at 4.2 K and the hyperfine and quadrupole interactions with the nearest-neighbour 27Al nuclei and with the 53Cr isotope have been investigated. The results show that Cr3+ has the point symmetry 3m, being subjected to the original trigonal expansion at the B sites, but inducing some distortion effects on its surroundings. Further, the isotropic hyperfine constant of the 27Al nuclei has been analysed in an independent bonding model, showing that there is appreciable transfer of unpaired spin to the aluminium ion due to covalency.

[1]  C. B. Carter,et al.  On the point group of stoichiometric spinel, MgO·Al2O3 , 1985 .

[2]  G. Wirtz,et al.  MgAl2O4 ion positions calculated for the F43m space group , 1984 .

[3]  P. Thompson,et al.  New symmetry and structure for spinel , 1983, Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences.

[4]  E. Samuelsen,et al.  The Space Group of Spinel Revisited , 1981 .

[5]  M. Tokonami,et al.  On the space group of spinel, MgAl2O4 , 1980 .

[6]  P. Smith Note on the space group of spinel minerals , 1978 .

[7]  P. Thompson,et al.  Multiple diffraction in spinel and the space‐group ambiguity , 1977 .

[8]  G. Thomas,et al.  Structural phase transition in the spinel MgA12O4 , 1977 .

[9]  F. Waldner,et al.  The inversion parameter with respect to the space group of MgAl2O4 spinels , 1976 .

[10]  A. Heuer,et al.  Further discussion on the space group of spinel , 1975 .

[11]  E. Samuelsen,et al.  On the space group of spinel , 1975 .

[12]  A. Leclerc,et al.  Electron-nuclear double resonance of 53Cr3+ in guanidinium aluminum sulfate hexahydrate , 1974 .

[13]  J. Henning,et al.  ESR Investigations of Nearest-Neighbor Cr 3+ -Cr 3+ Interactions in Cr-Doped Spinel MgAl 2 O 4 , 1973 .

[14]  B. Wanklyn,et al.  Hyperfine interactions and electron transfer between metal ions in Fe:LaAlO3 and Cr:LaAlO3 , 1973 .

[15]  A. Heuer,et al.  On the space group of MgAl2O4 spinel , 1973 .

[16]  J. Henning,et al.  An orthorhombic chromium-center in the spinel MgAl2O4 , 1973 .

[17]  Z. Chang,et al.  Pressure dependence of single‐crystal elastic constants and anharmonic properties of spinel , 1973 .

[18]  N. W. Grimes Antiferroelectricity among compounds with spinel structure , 1973 .

[19]  A. Manoogian,et al.  Electron-Nuclear Double Resonance ofCr3+53in Gallium Alums. II , 1972 .

[20]  N. W. Grimes 'Off-centre' ions in compounds with spinel structure , 1972 .

[21]  F. Waldner,et al.  A direct determination of cation disorder in MgAl2O4 spinel by ESR , 1972 .

[22]  N. W. Grimes Structural distortions in MgCr2O4 , 1971 .

[23]  N. W. Grimes,et al.  Correlation of Infra-Red Spectra with Structural Distortions in the Spinel Series Mg(CrxAl2-x)O4 , 1971 .

[24]  K. Müller,et al.  Covalency and hyperfine structure constant A of iron group impurities in crystals , 1969 .

[25]  D. Ballentyne,et al.  Visible and ultra-violet emission and absorption spectra of MgAl2O4:Cr , 1968 .

[26]  J. Thornley,et al.  Covalent bonding and magnetic properties of transition metal ions , 1966 .

[27]  J. S. Hyde ENDOR OF FREE RADICALS IN SOLUTION , 1965 .

[28]  S. B. Berger The Sign of the Trigonal Field Splitting of B‐Site Ions in Spinel , 1965 .

[29]  B. Mcgarvey Anisotropic Hyperfine Interaction of Cr53 in Chromium (III) Acetylacetonate , 1964 .

[30]  E. Brun,et al.  Die elektrische Quadrupolaufspaltung von Al27in Spinell MgAl2O4und Korund Al2O3: I. Paramagnetische Kernresonanz von Al27und Kationenverteilung in Spinell , 1962 .

[31]  W. Marshall,et al.  Theory of Transition Ion Complexes , 1961 .

[32]  J. Lambe,et al.  HYPERFINE SPECTRUM OF CHROMIUM 53 IN Al$sub 2$O$sub 3$ , 1961 .

[33]  W. Low,et al.  Paramagnetic Resonance Spectra of Chromium and Manganese in the Spinel Structure , 1959 .

[34]  H. Saalfeld,et al.  Kationenverteilung und Strukturbeziehungen in Mg-Al-Spinellen , 1958 .