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Green function method in the theory of ferromagnetic thin films
Vol. 3, No. 7
ABSTRACTS OF PAPERS TO APPEAR IN 3. PETS. CEEM. SOLIDS
The specific beats of silver have been calculated on Krebs’ model. These results have been discussed along with the earlier calculations on copper and gold published by one of us. It is found that Kr’eb.’ model is able to reproduce the experimental values remarkably well provided we consider the screening parameter as an adinstable constant. In the case of copper, its numerical value is given by the theory of Bohm and Pines and for gold by that of Thomas and Fermi. For silver it lies between the two theories. (Received 18 December 1964) (Revised 15 January 1965) 8.
ELECTRON SPIN RESONANCE OF Mn2~ Di Mg 251. H. B. Nudelman, S. H. Johnson and R. G. Barnes (Institute for Atomic Research and Department of Physics, Iowa State University, Ames, Iowa, U. S. A.).
2~has investigatedresonance in single spectrum crystals ofof Thebeen paramagnetic Mncubic semiconductor, Mg the 2SI, at 4. 2°Kand 9lOOMc/sec. The principal results are that g = 2.0048, the hYpyfine splitting constant A = 50.6 x l0~ cni , a~idthe cUbic splitting factor a = 7.14 x 10~cm These results are indicative of strong covalent bonding in this compound.
acceptor pair recomhinetion although it is not clear why two series of peaks are seen in this emission. The vacuum treatment alao removes nonreversibly another line ‘2c’ associated with an unknown donor. (Received 22 January 1965) 10. GREEN FUNCTION METHOD Di THE THEORY OF FERROMAGNETIC THIN FILMS. A. Corciovel and G. Clobanu (Institute for Atomic Physics, Bucharest, Rumania and InstItute of Physics, Bucharest, Rumania). A thin film of atomic spins arranged in a simple cubic lattice, the Haw’fltonlan of which contains the exchange and magnetic anisotropy terms is considered. The dependence of the magnetization of the thin films on the temperahire, for various numbers of monatomic layers of the thin film i.e studied by means of doubletime-temperature-dependent Green function. A which valid in for the the entire range of temperatures generalisformula magnetization is obtained and which depends on the thickness of the thin film. In the case of the low temperatures the results of the spin-wave theory are obtained. (Received 26 January 1965)
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(Received 18 January 1965) 9.
THE EFFECTS OF LOW TEMPERATURE HEAT TREATMENTS ON THE CONDUCTWITY AND PHOTOLUMINESCENCE OF CdS. E. T. Handelman and D. G. Thomas (Bell Telephone Laboratories, Inc., Murray Hill, New Jersey, U. S. A.).
Controlled reversible changes of stolchiometric defect concentrations have been produced In single crystal CdS by heating in vacuum (i.e. low Cd pressure) at 500-600°C, to yield low conductivity material, and by heating in saturated Cd vapor to restore the original high conductivity state. It is concluded that the conductivity is reduced as a result of compensation by cadmium vacancy acceptors. The well defined conductivity changes have been correlated with corresponding changes In the fluorescent spectra taken at 20°K or below. The acceptor produces a sharp line Il, and simultanelusly broad edge emission appears. The latter may arise from donor-
11. A ONE-PARAMETER TREATMENT OF ANRARMONIC SPECIFIC HEAT. J. L. Feldman, G. K. Horton and J. B. Lurie (Department of Physics, Rutgers University, New Brunswick, N.J., U.S.A.). This paper develops an approximate method of calculating anharmonic corrections to the calorimetric properties of solids from known values of the corresponding harmonic quantities. It is assumed that anharmonic effects may be represented by simple temperahire and frequency dependent shifts, first used by Barron and Overton, in the frequencies appearing in the free energy or the entropy. Numerical results for 5a_5n and C~ C~,based on published harmonic calculations are given for several substances. It is found that 5a_ 5h begins to depart from a linear T dependence at T/8— 3. A discussion is given of how our results may be used as a refinement of Tosi and Fumi’s method for analyzing experimental calorimetric data. Using our approach, it is demonstrated that the oscillation in C~ C~,found in calculations recently reported by Overton for a special model -
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ABSTRACTS OF PAPERS TO APPEAR IN 3. PETS. CEEM. SOLIDS
The specific beats of silver have been calculated on Krebs’ model. These results have been discussed along with the earlier calculations on copper and gold published by one of us. It is found that Kr’eb.’ model is able to reproduce the experimental values remarkably well provided we consider the screening parameter as an adinstable constant. In the case of copper, its numerical value is given by the theory of Bohm and Pines and for gold by that of Thomas and Fermi. For silver it lies between the two theories. (Received 18 December 1964) (Revised 15 January 1965) 8.
ELECTRON SPIN RESONANCE OF Mn2~ Di Mg 251. H. B. Nudelman, S. H. Johnson and R. G. Barnes (Institute for Atomic Research and Department of Physics, Iowa State University, Ames, Iowa, U. S. A.).
2~has investigatedresonance in single spectrum crystals ofof Thebeen paramagnetic Mncubic semiconductor, Mg the 2SI, at 4. 2°Kand 9lOOMc/sec. The principal results are that g = 2.0048, the hYpyfine splitting constant A = 50.6 x l0~ cni , a~idthe cUbic splitting factor a = 7.14 x 10~cm These results are indicative of strong covalent bonding in this compound.
acceptor pair recomhinetion although it is not clear why two series of peaks are seen in this emission. The vacuum treatment alao removes nonreversibly another line ‘2c’ associated with an unknown donor. (Received 22 January 1965) 10. GREEN FUNCTION METHOD Di THE THEORY OF FERROMAGNETIC THIN FILMS. A. Corciovel and G. Clobanu (Institute for Atomic Physics, Bucharest, Rumania and InstItute of Physics, Bucharest, Rumania). A thin film of atomic spins arranged in a simple cubic lattice, the Haw’fltonlan of which contains the exchange and magnetic anisotropy terms is considered. The dependence of the magnetization of the thin films on the temperahire, for various numbers of monatomic layers of the thin film i.e studied by means of doubletime-temperature-dependent Green function. A which valid in for the the entire range of temperatures generalisformula magnetization is obtained and which depends on the thickness of the thin film. In the case of the low temperatures the results of the spin-wave theory are obtained. (Received 26 January 1965)
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(Received 18 January 1965) 9.
THE EFFECTS OF LOW TEMPERATURE HEAT TREATMENTS ON THE CONDUCTWITY AND PHOTOLUMINESCENCE OF CdS. E. T. Handelman and D. G. Thomas (Bell Telephone Laboratories, Inc., Murray Hill, New Jersey, U. S. A.).
Controlled reversible changes of stolchiometric defect concentrations have been produced In single crystal CdS by heating in vacuum (i.e. low Cd pressure) at 500-600°C, to yield low conductivity material, and by heating in saturated Cd vapor to restore the original high conductivity state. It is concluded that the conductivity is reduced as a result of compensation by cadmium vacancy acceptors. The well defined conductivity changes have been correlated with corresponding changes In the fluorescent spectra taken at 20°K or below. The acceptor produces a sharp line Il, and simultanelusly broad edge emission appears. The latter may arise from donor-
11. A ONE-PARAMETER TREATMENT OF ANRARMONIC SPECIFIC HEAT. J. L. Feldman, G. K. Horton and J. B. Lurie (Department of Physics, Rutgers University, New Brunswick, N.J., U.S.A.). This paper develops an approximate method of calculating anharmonic corrections to the calorimetric properties of solids from known values of the corresponding harmonic quantities. It is assumed that anharmonic effects may be represented by simple temperahire and frequency dependent shifts, first used by Barron and Overton, in the frequencies appearing in the free energy or the entropy. Numerical results for 5a_5n and C~ C~,based on published harmonic calculations are given for several substances. It is found that 5a_ 5h begins to depart from a linear T dependence at T/8— 3. A discussion is given of how our results may be used as a refinement of Tosi and Fumi’s method for analyzing experimental calorimetric data. Using our approach, it is demonstrated that the oscillation in C~ C~,found in calculations recently reported by Overton for a special model -
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