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  • 1
    Electronic Resource
    Electronic Resource
    Fe^3^+ in shocked olivine crystals of the ALHA 77005 meteorite
    Amsterdam : Elsevier
    Earth and Planetary Science Letters 67 (1984), S. 162-166 
    Details
    ISSN: 0012-821X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0012-821X(84)90111-0
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  • 2
    Electronic Resource
    Electronic Resource
    Influence of phosphorus substitution on Mn"0"."6"3Cr"0"."3"7As
    Amsterdam : Elsevier
    Journal of Magnetism and Magnetic Materials 94 (1991), S. 347-354 
    Details
    ISSN: 0304-8853
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0304-8853(91)90097-T
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  • 3
    Electronic Resource
    Electronic Resource
    Electric field gradients and asymmetry parameters of Fe^3^+, Mn^2^+, Cr^3^+, and Mg^2^+ in Mg"2SiO"4
    Amsterdam : Elsevier
    Journal of Molecular Structure 58 (1980), S. 215-220 
    Details
    ISSN: 0022-2860
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0022-2860(80)85023-X
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  • 4
    Electronic Resource
    Electronic Resource
    Polarized optical absorption spectra of synthetic chromium doped Mg2SiO4 (forsterite) (1991)
    Springer
    Physics and chemistry of minerals 18 (1991), S. 37-39 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Polarized optical absorption measurements were carried out on three single crystals of Mg2SiO4 (forsterite), differently doped with Cr. Two crystals containing average 0.013 and 0.027 weight% Cr, respectively, were pulled from the melt in air, whereas one crystal containing average 0.08 weight% Cr was pulled from the melt in an argon atmosphere. The absorption spectra of the three crystals agree with each other although the intensity of single absorption bands varies significantly. In all γ-polarized patterns a sharp absorption line around 18000cm-1 (550 nm) appears. Conjectures are presented to assign this line to the lasing center in Cr doped forsterite which very likely exists as Cr4+ at the fourfold coordinated Si site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00199041
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  • 5
    Electronic Resource
    Electronic Resource
    Modulations in incommensurate (Ca1–xSrx)2MgSi2O7 single crystals (1998)
    Springer
    Physics and chemistry of minerals 26 (1998), S. 128-134 
    Details
    ISSN: 1432-2021
    Keywords: Key words strontium åkermanite ; single crystals ; modulated structure ; electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract  Single crystals of (Ca1–xSrx)2MgSi2O7 slightly doped with 1000 ppm Mn2+ and with x ranging from 0.04 to 0.32 were grown from the melt in a mirror furnace applying the Czochalski technique. Transmission electron microscopy (TEM) revealed incommensurately modulated structures at room-temperature for all compositions in accordance with earlier studies by electron paramagnetic resonance (EPR). Electron diffraction patterns clearly show satellite reflections typical for two-dimensional modulation, and their successive destabilization with increasing Sr content. The modulation is of tartan-like appearance. Beyond a Sr/(Sr+Ca) ratio of about 0.32 the synthesis of stable solid solution åkermanite type crystals was proved not to be feasible, indicating the existence of a miscibility gap in the Sr åkermanite system. As presumed from the diffuse scattering around the satellite reflections, and suggested more conclusively by crystallographic processing of high resolution EM images the Sr ions incorporated into the incommensurate crystal phase are distributed in an ordered fashion and are partly adapted to the displacive modulation of the pure åkermanite. This means, occupational modulation even makes a contribution to the overall modulation characteristics in (Ca1–xSrx)2 MgSi2O7.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690050169
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  • 6
    Electronic Resource
    Electronic Resource
    Electron paramagnetic resonance and ENDOR studies of Cr3+ - Al3+ pairs in forsterite (1983)
    Springer
    Physics and chemistry of minerals 9 (1983), S. 95-101 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract The electron paramagnetic resonance (EPR) spectrum of Cr3+ in synthetic crystals of forsterite consists primarily of lines of Cr3+ “isolated” at the M1 and M2 positions in a “perfect” crystal environment without local charge compensation. In addition it shows two nonequivalent superhyperfine-split sextets with different intensities which are due to strong interaction of the Cr3+ electron spin S (S=3/2) with an adjacent nuclear spin I(I=5/2). Electron nuclear double resonance (ENDOR) experiments revealed that the sextets result from Cr3+ (M1) - Al3+ and Cr3+ (M2) - Al3+ pairs, Al being located at adjacent tetrahedral Si sites. The g, D, A, and A′ tensor components of the Cr3+ - Al3+ pairs have been determined at room temperature. The values of the pairs are distinct although they are not very different from the corresponding data of “isolated” Cr3+. From the intensities of the EPR spectra the relative concentration of the Cr3+ - Al3+ pairs with respect to “isolated” Cr3+ has been estimated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00308364
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  • 7
    Electronic Resource
    Electronic Resource
    Electron spin resonance of trivalent chromium in forsterite, Mg2SiO4 (1977)
    Springer
    Physics and chemistry of minerals 1 (1977), S. 371-378 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract The electron spin resonance (ESR) spectrum of Cr3+ in a synthetic single crystal of forsterite doped with Cr2O3 was studied at room temperature in the X-band frequency range. The dependence of the observed spectra on the crystal orientation with respect to the applied magnetic field was investigated. The ESR spectra are described by the spin Hamiltonian $$H = \beta HgS + D(S_Z^{\text{2}} - {\text{1/3}}S{\text{(}}S{\text{ + 1)) + }}E{\text{(}}S_x^{\text{2}} - S_y^{\text{2}} {\text{)}}$$ with S=3/2. The spin resonance reveals that the chromium ions are located at both the M1 and M2 positions. Other possible substitutional or interstitial Cr3+ positions may be possible, but were not observed. The site occupancy numbers of Cr3+ at M1 and M2 are roughly 1.2×10−4 and 0.8×10−4, respectively, assuming that chromium is oxidized completely. The preference of the chromium ions for M1 was interpreted qualitatively in terms of crystal field criteria. The rhombic and axial spin Hamiltonian parameters, D and E, and the directions of the magnetic axes obtained for M1 and M2 are consistent with the respective oxygen coordination polyhedra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00308846
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  • 8
    Electronic Resource
    Electronic Resource
    Electron paramagnetic resonance and polarized optical absorption spectra of Ni2+ in synthetic forsterite (1988)
    Springer
    Physics and chemistry of minerals 15 (1988), S. 383-389 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract The investigated Ni doped forsterite was grown with the floating zone technique. The EPR spectra were taken at room temperature using both 9.5 and 35 GHz. All specimens show EPR signals resulting from Mn2+ at M2 and Fe3+ at M1, M2, and Si positions. Ni2+ EPR signals are observed at 35 GHz but not at 9.5 GHz. The Ni2+ spectra are described by the spin Hamiltonian $$H = \beta SgB + D\left( {S_{\text{z}}^{\text{2}} - \left( {S + 1} \right)S/3} \right) + E\left( {S_{\text{x}}^{\text{2}} - S_{\text{y}}^{\text{2}} } \right)$$ with S=1. The EPR parameters obtained are: D=−39.56 cm−1, E=−0.58 cm−1, g x=2.194, g y=2.160, g z=2.188. Polarized optical absorption spectra of Ni2+ were taken at room and liquid nitrogen temperature covering the range from 5500 to 42000 cm−1. The spectra are nearly independent of the polarization of light. Both EPR and optical spectra reveal that Ni2+ is ordered into M1. The local symmetry of the Ni(M1) complex is described by the point group D 2h with the main symmetry axis along a. Heating experiments in air up to 1000° C and three days indicated no change in the Ni ordering in this synthetic sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00311043
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  • 9
    Electronic Resource
    Electronic Resource
    29Si and 27Al MAS NMR spectroscopy of mullite (1991)
    Springer
    Physics and chemistry of minerals 18 (1991), S. 47-52 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract A 29Si and 27Al magic angle spinning nuclear magnetic resonance study is reported for differently synthesized mullites. The 29Si MAS NMR spectra of all samples are essentially identical. They consist of a main resonance at -86.8 ppm, a shoulder around -90 ppm and a second resonance at -94.2 ppm. The main resonance is interpreted as being due to a sillimanite-type geometry around Si and the second one is tentatively assigned to a Si environment typical for mullite. The 27Al MAS NMR spectra of sinter- and fused-mullite measured at different Larmor frequencies revealed clearly the presence of three distinct Al sites in mullite, i.e. of octahedral (M1), tetrahedral (M2) and distorted tetrahedral (Al*) sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00199043
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  • 10
    Electronic Resource
    Electronic Resource
    NMR of ^2^9Si and ^2^5Mg In Mg"2SiO"4 with dynamic polarization technique
    Amsterdam : Elsevier
    Physics Letters A 66 (1978), S. 150-152 
    Details
    ISSN: 0375-9601
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0375-9601(78)90023-3
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