Optical absorption spectrum of Cr3+ ions in sodium ammonium sulphate dihydrate single crystal
TL;DR: In this paper, the optical absorption spectrum of Cr3+ ions doped in sodium ammonium sulphate dihydrate single crystal has been studied both at room and liquid nitrogen temperatures.
Abstract: Optical absorption spectrum of Cr3+ ions doped in sodium ammonium sulphate dihydrate single crystal has been studied both at room and liquid nitrogen temperatures The observed bands were explained satisfactorily assuming octahedral symmetry for the Cr3+ ion in the crystal The crystal field parameters Dq = 1750 cm−1, B = 735 cm−1 and C = 3220 cm−1 are found to give a good fit to the observed band positions
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TL;DR: In this paper, electron paramagnetic resonance and dielectric measurements carried out for Mn 2+ -doped sodium ammonium sulphate dihydrate are presented, and it is shown that the measured spin-Hamiltonian parameters can be consistently explained in terms of the superposition model of Newman taking into account local distortions caused by the introduction of the impurity ion.
Abstract: Electron paramagnetic resonance and dielectric measurements carried out for Mn 2+ -doped sodium ammonium sulphate dihydrate are presented. It is shown that in addition to the main ferroelectric-phase transition, one also detects a small anomaly in the temperature dependence of the dielectric susceptibility and the corresponding change in the slope of the temperature dependence of the spin-Hamiltonian parameter D at about 190 K. It was found that the doping leads to the decrease of the transition temperature estimated to be about 3.7 K. It is also shown that the measured spin-Hamiltonian parameters can be consistently explained in terms of the superposition model of Newman taking into account local distortions caused by the introduction of the impurity ion. A model for the charge compensation mechanism is suggested.
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TL;DR: In this paper, a simultaneous neutron diffraction and neutron inelastic scattering experiment on sodium ammonium sulphate dihydrate has been carried out in the temperature range 300 to 20 K.
Abstract: A simultaneous neutron diffraction and neutron inelastic scattering experiment on sodium ammonium sulphate dihydrate has been carried out in the temperature range 300 to 20 K. The neutron powder diffraction (NPD) spectra correlate with those found previously using X-ray diffraction dilatometry The IINS spectra are reported for the first time. For the temperature range from 160 to 200 K, they indicate the existence of a glassy transition or an instability caused by soft optic modes. The generalized phonon density of states G(ω) is also discussed. The observed bands are ascribed to particular vibrational modes of the crystal as a whole and of NH 4 + , SO 4 2- and H 2 O groups.
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TL;DR: In this paper, the absorption spectra of crystalline hydrates of the first transition group ions have been measured with polarized light at room temperature, and with unpolarized light at a series of lower temperatures.
Abstract: The absorption spectra of crystalline hydrates of the first transition group ions have been measured with polarized light at room temperature, and with unpolarized light at a series of lower temperatures. Some new data on solution spectra have also been obtained. The values of Dq for these compounds are obtained, and are used to explain irregularities in the heats of hydration of the ions. The temperature dependence of the spectra shows that the transitions are vibration‐induced electric‐dipole transitions for the most part. The dichroism has been used to resolve some of the bands and to determine the effect of noncubic components of the crystal field.
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