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  • 1
    Electronic Resource
    Electronic Resource
    Dielectric properties of titanium and gadolinium doped MgO single crystals (1982)
    Springer
    Applied physics 29 (1982), S. 29-32 
    Details
    ISSN: 1432-0630
    Keywords: 66 ; 72.20 ; 77.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The dielectric properties of titanium doped magnesium oxide (Ti/MgO) and gadolinium doped magnesium oxide (Gd/MgO) single crystals have been measured at room temperature over the frequency range 500 Hz to 50 kHz. For both the crystals, the dielectric constantɛ′ is found to be independent of frequency and the ac conductivity Re{σae} agrees well with the relation Re{σae}∫Ω n ,Ω being the angular frequency with n=0.84±0.05 for Ti/MgO andn=0.81±0.03 for Gd/MgO. The data fits well with the relationɛ″∫Ω n−1(n〈1),ɛ″ being the dielectric loss factor. An explanation may be found on the basis of the hopping phenomenon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00618112
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  • 2
    Electronic Resource
    Electronic Resource
    Microwave dielectric properties of Ti4+/MgO and Ni2+/MgO (1985)
    Springer
    Applied physics 36 (1985), S. 63-65 
    Details
    ISSN: 1432-0630
    Keywords: 66 ; 72.20 ; 77.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The dielectric properties of titanium-doped magnesium oxide (Ti/MgO) and nickel-doped magnesium oxide (Ni/MgO) single crystals have been measured in the range of temperature from 300 to 450 K at the microwave frequency of 9.31 GHz. For both crystals the dielectric properties are found similar. From the conductivity data, the activation energy in the measured temperature region has been estimated to be 0.15 eV. The values of the temperature dependence (ε′−1)−1(ε′+2)−1 (∂ε′/∂T) p have been calculated. The data confirms the Bosmann and Havinga postulate that, for materials in which the dielectric constant;ε′ is less than 20 the temperature dependence should be positive.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00616463
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  • 3
    Electronic Resource
    Electronic Resource
    High frequency dielectric constant of dry wood (1984)
    Springer
    Journal of materials science 3 (1984), S. 521-522 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00720989
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  • 4
    Electronic Resource
    Electronic Resource
    ESR line broadening in Cr3+/MgO at liquid helium temperatures (1980)
    Springer
    Journal of materials science 15 (1980), S. 3041-3046 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Line broadening has been observed at 9 GHz in the ESR absorption spectrum of Cr3+ in MgO in the liquid helium temperature range, for a range of Cr3+ concentrations from 800 7400 ppm. The broadened linewidths at 4.2 K are about two times larger than those at 77 K and depend on polar angle. The lineshapes are Gaussian, in contrast to the Lorentzian lineshape between 293 and 77 K. The broadening is interpreted by the combined effects of strain, due to the charge misfit of Cr3+ and the host cation, and temperature which causes both exchange striction and departure from the cubic symmetry to a lower symmetry. Analysis of the linewidth data gives ΔD=(5.25±0.40)×10−4 cm−1 and confirms that the total linewidth, ΔH t, is given by ΔH t=ΔH 0+∥(2ΔD/gβ) cos θ H∥ where ΔH 0 is the linewidth independent of concentration, temperature and polar angle, θ H.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00550373
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  • 5
    Electronic Resource
    Electronic Resource
    Electron spin resonance linewidths of Co2+ in magnesium oxide (1980)
    Springer
    Journal of materials science 15 (1980), S. 903-908 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Electron spin resonance linewidths of Co2+ in single-crystal MgO at 9 GHz were examined experimentally and theoretically for a range of Co2+ concentration from 310 to 9900 ppm. In contrast to the behaviour expected from dipolar broadening, the experimental peak-to-peak linewidth for the octed hyperfine lines were about twelve to fifty times less than the calculated dipolar linewidths according to temperature and concentrations. The peak-to-peak linewidths as determined experimentally increase from 0.8 mT at 310 ppm Co2+ to 4.0 mT at 9900 ppm Co2+ at a polar angle θ H= O° and at 20 K. Peak-to-peak linewidths independent of polar angle but strongly dependent on temperature and slightly dependent on concentrations were observed. The ratio of moments M 4 1/4 /M 2 1/2 derived from the experimental data lay between 1.35 to 1.44 and the lineshapes were markedly Lorentzian in the range of temperature measured. The data suggest that Co2+ entered the lattice substitutionally, occupying magnesium sites, that the linewidths were determined, after exchange energy, over the whole concentration range examined and that the exchange energy whose values lay between 6 and 77 GHz, varied linearly with concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00552101
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  • 6
    Electronic Resource
    Electronic Resource
    Exchange energies of iron group ions in single crystal MgO (1980)
    Springer
    Journal of materials science 15 (1980), S. 1866-1867 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00550610
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  • 7
    Electronic Resource
    Electronic Resource
    The ESR spectrum of Gd3+/MgO (1981)
    Springer
    Journal of materials science 16 (1981), S. 633-637 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Electron spin resonance studies have been made at 9.1 GHz on Gd3+/MgO single crystals grown by electrofusion and containing low gadolinium concentrations. A single isotropic line having g=1.992±0.00024 was observed in contrast to the seven line spectrum reported by Abraham. The experimental peak-to-peak linewidth for the −1/2↔+1/2 transition at 293 K was 0.3 mT and was independent of polar angle. This was nearly one hundred times less than the calculated dipolar linewidth and analysis verified that the lineshape was Lorentzian indicating exchange narrowing. The linewidth was independent of temperature from 4.2 to 293 K and the exchange energy derived for a gadolinium concentration of 310 ppm was 15 GHz. A discussion is given of the cubic field splittings of Gd3+ in oxide crystals and a comparison made of the exchange energies of transition group ions in the MgO lattice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00552201
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  • 8
    Electronic Resource
    Electronic Resource
    Electron spin resonance linewidths of Cr3+ in magnesium oxide (1979)
    Springer
    Journal of materials science 14 (1979), S. 2853-2858 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Electron spin resonance linewidths of Cr3+ in single crystal MgO at 9 GHz and 35 GHz were examined experimentally and theoretically for a range of Cr3+ concentrations. In contrast to the behaviour expected from dipolar broadening the experimental peak-to-peak linewidth for the 1/2 to−1/2 transition, which had a value of about 0.5 mT at 293 K, was independent of both polar angle and concentration over the range from 800 p.p.m. Cr to 15 100 p.p.m. Cr. The calculated dipolar linewidths exceeded those observed by factors of over one hundred; the ratio of momentsM 4 1/2 /M 2 1/2 derived from the experimental data lay between 1.33 and 1.39 and the lineshapes were markedly Lorentzian. The data suggested that Cr3+ entered the lattice substitutionally, occupying magnesium sites, that the linewidths were determined by exchange narrowing over the whole concentration range examined and that the exchange energy, whose values lay between 4 GHz and 100 GHz, varied linearly with concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00611465
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  • 9
    Electronic Resource
    Electronic Resource
    ESR line broadening of Fe3+ in Fe/MgO at low temperatures (1980)
    Springer
    Journal of materials science 15 (1980), S. 2647-2650 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Electron spin resonance linewidths of Fe3+ in single crystal MgO were examined at 9 GHz for crystals having iron concentrations of 2300 ppm and 4300 ppm over the temperature range 293 to 4.2 K. For the + 1/2 → −1/2 transition the linewidth remains constant from 293 to about 15 K, below which line broadening occurs. From 15 to 4.2 K the linewidth increases steadily without any change in the g value of the line. At 4.2 K the width of the line is about 3.7 times larger than at 77 K for each concentration. The lineshapes are Lorentzian over the whole temperature range examined and the data suggested that the effects observed below 15 K were due to non-secular line broadening mechanisms (the “10/3” effect) originally proposed by Anderson and Weiss.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00550771
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  • 10
    Electronic Resource
    Electronic Resource
    The ESR spectrum of Gd3+/MgO (1981)
    Springer
    Journal of materials science 16 (1981), S. 633-637 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Electron spin resonance studies have been made at 9.1 GHz on Gd3+/MgO single crystals grown by electrofusion and containing low gadolinium concentrations. A single isotropic line havingg=1.992±0.00024 was observed in contrast to the seven line spectrum reported by Abraham. The experimental peak-to-peak linewidth for the −1/2↔+1/2 transition at 293 K was 0.3 mT and was independent of polar angle. This was nearly one hundred times less than the calculated dipolar linewidth and analysis verified that the lineshape was Lorentzian indicating exchange narrowing. The linewidth was independent of temperature from 4.2 to 293 K and the exchange energy derived for a gadolinium concentration of 310 ppm was 15 GHz. A discussion is given of the cubic field splittings of Gd3+ in oxide crystals and a comparison made of the exchange energies of transition group ions in the MgO lattice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02402780
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