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55Mn nuclear magnetic resonance in Mn2Sb
ii
ABSTRACTS OF ARTICLES TO BE PUBLISHED IN THE J. PHYS. CHEM. SOLIDS
4.
ELECTRONIC AND VIBRATIONAL SPECTRA OF CrO~IN CESIUM HALIDE LATTICES S. Radhakrishna and K. Hariharan, Department of Physics, Indian Institute of Technology, Madras-600 036, India.
The electronic spectra of CrO~ions embedded in cesium halide lattices show two well defined bands due to dipole allowed transitions along with some weak bands due to forbidden transitions. All the above bands are interpreted in terms of transitions within molecular orbital levels using the Ballhausen and Liehr schema. it is observed that superposed on the electronic transitions there is a vibrational fine structure which arises due to the coupling between the electronic transitions and the totally symmetric stretching frequency of the ion. IR absorption spectrum of Analar grade CsI : CrO~shows seven lines, whereas Specoure CsI : CrO~shows five lines. The above spectra are interpreted on the basis of different local symmetries of CrO~ions in the lattice. Received 18 Septemb’er 1978 Revised 21 March 1979 5.
STEADY STATE AND TRANSIENT FLUORESCENCE STUDIES OF CaF2 ~ SINGLE CRYSTALS
Str. Erou lancu Nicolae 32 B, Sect. 2, Romania. Some analytical models of quiescent hot electron distribution are extended to the transient conditions, in order to describe the response of hot electrons to step changes in the magnitude of an electric field. These models apply to semiconductors having one or several equivalent energy minima in the conduction band, and isotropic lattice scattering due to low-energy acoustic phonons (elastic in-valley scattering) and to high energy single-level acoustic phonons (inelastic inter-valley scattering or dispersionless optical phonons (inelastic in-valley scattering). Step changes in the field magnitude are considered with respect to the time and space (one-dimensional) variables, separately. In both cases, the spherically-symmetrical term f0 of the electron distribution function may be expressed using a Laguerre polynomial expansion in the energy variable. For a positive step change in field magnitude, transient electron drift velocities in excess of the steady-state “scattering-limited” values are found in both silicon and germanium. Received 21 November 1978 7.
A. Sivaram, H. Jagannath, D. Ramachandra Rao and Putcha Venkateswarlu, Lasers and Spectroscopy Laboratory, Department of Physics, Indian Institute of Technology, Kanpur, India. The steady statebeen and studied transientusing fluorescence 3~ have Ar~and Nspectra of CaF2 : jy~ 2 lasers in the temperature range 77—673 K and in the wavelength region 4500—9000 A. The spectra show the presence of two types of centers (type A and type B) with decay times of 1.3 and 3.5 msec. The observed spectrum is mostly due 4Fto type6HA centers. 4F Three 6H new6Fgroups of fluorescence 912 — 1112, 912 ( 912, 1112) and 4F 6H 6F 912 —( 712, 912) have been observed for type A centers, and a tentative assignment 6H 6H 6F of the positions 6H 6Fof the Stark levels 1112 ( 912, 1112) and ( 712 912) has been made. The change in the intensity of the transitions with temperature and excitation wavelength are discussed. —
,
55Mn NUCLEAR MAGNETIC RESONANCE IN Mn 2Sb K.V.S. Rama Rao, S.L. Pinjare, T. Rajasekharan and C. Ramasastry, Department of Physics, Indian Institute of Technology, Madras600036, India.
The observation of NMR signals from ~Mn nuclei in Mn2Sb has been reported. A temperature variation study of the domain and domain wall signals in Mn2Sb confirms that the magnetization is aligned parallel to the c-axis at temperatures higher than 240 K and that it is in the basal plane below 240 K. The temperature dependence of the anisotropy in the hyperfine field at the Mn(I) and Mn (II) sites has been determined. Received 30 May 1978 Revised 21 March 1979
,
Received 5 October 1979 6.
Vol. 32, No. 12
THE INFLUENCE OF ABRUPT ELECTRIC FIELD VARIATIONS ON THE DISTRIBUTION FUNCTION OF HOT ELECTRONS A. Mthnea and Ioana Guräu, Research Institute for Electronic Components, ICCE Bucure~ti,
8.
EXCHANGE-STRICTION OF RARE EARTH—Al2 LAVES PHASE COMPOUNDS F. Pourarian, Department of Physics, The University of Southampton, England. The exchange-striction of the cubic Laves phase
compounds R—A12 (R = Gd, Tb, Dy, and Ho) has been determined at 0 K from measurements of thermal expansion. The results are interpreted in terms of rare earth sublattice (R—R) interactions, using the molecular field approximation. It is found that the signs of the
ABSTRACTS OF ARTICLES TO BE PUBLISHED IN THE J. PHYS. CHEM. SOLIDS
4.
ELECTRONIC AND VIBRATIONAL SPECTRA OF CrO~IN CESIUM HALIDE LATTICES S. Radhakrishna and K. Hariharan, Department of Physics, Indian Institute of Technology, Madras-600 036, India.
The electronic spectra of CrO~ions embedded in cesium halide lattices show two well defined bands due to dipole allowed transitions along with some weak bands due to forbidden transitions. All the above bands are interpreted in terms of transitions within molecular orbital levels using the Ballhausen and Liehr schema. it is observed that superposed on the electronic transitions there is a vibrational fine structure which arises due to the coupling between the electronic transitions and the totally symmetric stretching frequency of the ion. IR absorption spectrum of Analar grade CsI : CrO~shows seven lines, whereas Specoure CsI : CrO~shows five lines. The above spectra are interpreted on the basis of different local symmetries of CrO~ions in the lattice. Received 18 Septemb’er 1978 Revised 21 March 1979 5.
STEADY STATE AND TRANSIENT FLUORESCENCE STUDIES OF CaF2 ~ SINGLE CRYSTALS
Str. Erou lancu Nicolae 32 B, Sect. 2, Romania. Some analytical models of quiescent hot electron distribution are extended to the transient conditions, in order to describe the response of hot electrons to step changes in the magnitude of an electric field. These models apply to semiconductors having one or several equivalent energy minima in the conduction band, and isotropic lattice scattering due to low-energy acoustic phonons (elastic in-valley scattering) and to high energy single-level acoustic phonons (inelastic inter-valley scattering or dispersionless optical phonons (inelastic in-valley scattering). Step changes in the field magnitude are considered with respect to the time and space (one-dimensional) variables, separately. In both cases, the spherically-symmetrical term f0 of the electron distribution function may be expressed using a Laguerre polynomial expansion in the energy variable. For a positive step change in field magnitude, transient electron drift velocities in excess of the steady-state “scattering-limited” values are found in both silicon and germanium. Received 21 November 1978 7.
A. Sivaram, H. Jagannath, D. Ramachandra Rao and Putcha Venkateswarlu, Lasers and Spectroscopy Laboratory, Department of Physics, Indian Institute of Technology, Kanpur, India. The steady statebeen and studied transientusing fluorescence 3~ have Ar~and Nspectra of CaF2 : jy~ 2 lasers in the temperature range 77—673 K and in the wavelength region 4500—9000 A. The spectra show the presence of two types of centers (type A and type B) with decay times of 1.3 and 3.5 msec. The observed spectrum is mostly due 4Fto type6HA centers. 4F Three 6H new6Fgroups of fluorescence 912 — 1112, 912 ( 912, 1112) and 4F 6H 6F 912 —( 712, 912) have been observed for type A centers, and a tentative assignment 6H 6H 6F of the positions 6H 6Fof the Stark levels 1112 ( 912, 1112) and ( 712 912) has been made. The change in the intensity of the transitions with temperature and excitation wavelength are discussed. —
,
55Mn NUCLEAR MAGNETIC RESONANCE IN Mn 2Sb K.V.S. Rama Rao, S.L. Pinjare, T. Rajasekharan and C. Ramasastry, Department of Physics, Indian Institute of Technology, Madras600036, India.
The observation of NMR signals from ~Mn nuclei in Mn2Sb has been reported. A temperature variation study of the domain and domain wall signals in Mn2Sb confirms that the magnetization is aligned parallel to the c-axis at temperatures higher than 240 K and that it is in the basal plane below 240 K. The temperature dependence of the anisotropy in the hyperfine field at the Mn(I) and Mn (II) sites has been determined. Received 30 May 1978 Revised 21 March 1979
,
Received 5 October 1979 6.
Vol. 32, No. 12
THE INFLUENCE OF ABRUPT ELECTRIC FIELD VARIATIONS ON THE DISTRIBUTION FUNCTION OF HOT ELECTRONS A. Mthnea and Ioana Guräu, Research Institute for Electronic Components, ICCE Bucure~ti,
8.
EXCHANGE-STRICTION OF RARE EARTH—Al2 LAVES PHASE COMPOUNDS F. Pourarian, Department of Physics, The University of Southampton, England. The exchange-striction of the cubic Laves phase
compounds R—A12 (R = Gd, Tb, Dy, and Ho) has been determined at 0 K from measurements of thermal expansion. The results are interpreted in terms of rare earth sublattice (R—R) interactions, using the molecular field approximation. It is found that the signs of the