Abstract
EPR experimental results obtained for SASeD doped with Cr 3+ are reported with special emphasis on those observations which reveal the effect of soft modes i.e. the temperature dependence of the DZZ spinHamiltonian parameter and the temperature dependence of the EPR linewidth. An extension of the twosublattice model, previously developed and tested for SASD, to include lattice vibrations is presented. The obtained spectrum of bound excitations for the system investigated supports the idea that soft modes contribute to the phase transition at TC = 175 K. The anomaly detected at T1 = 150 K has only a quasisoft mode character and the anomaly detected at T2 = 280 K cannot be related to the effect of soft modes.
Highlights
Sodium ammonium selenate dihydrate (SASeD) crystals have been investigated for many years
The effect of soft modes in the phase transition of SASeD has not been described so far. It is the aim of this paper to report how the effect of soft modes reflects in the temperature dependence of the EPR spectrum of SASeD doped with Cr3+ and how the theory developed by us and described in [4] can be extended to include dipole interactions with the crystal lattice
The EPR spectrum of SASeD doped with Cr3+ is shown in figure 1
Summary
Sodium ammonium selenate dihydrate (SASeD) crystals have been investigated for many years. Perhaps the most complete account of the properties of SASeD is given in the paper by Aleksandrov et al [1]. Tc = 175 K the crystal becomes ferroelectric. The effect of soft modes in the phase transition of SASeD has not been described so far. It is the aim of this paper to report how the effect of soft modes reflects in the temperature dependence of the EPR spectrum of SASeD doped with Cr3+ and how the theory developed by us and described in [4] can be extended to include dipole interactions with the crystal lattice
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