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EPR experimental results obtained for SASeD doped with Cr³⁺ are reported with special emphasis on those observations which reveal the effect of soft modes i.e. the temperature dependence of the DZZ spin- Hamiltonian 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. Експериментальнi результати дослiджень SASeD легованого Cr³⁺ методами ЕПР поданi з наголосом на виявлений вплив м’яких мод, а саме температурної залежностi спiн-гамiльтонового параметра DZZ i ширини лiнiї ЕПР. Двопiдграткову модель, яка була запропонована i апробована раніше для SASD, узагальнено в напрямку врахування коливань гратки. Отриманий спектр зв’язаних коливань системи пiдтверджує iдею про вклад м’яких мод у фазовий перехiд при Tc = 175 K. Аномалiя, виявлена при T1 = 150 K має характер квазiм’якої моди, а аномалiю при T2 = 280 K не можна вiднести до ефекту м’яких мод.

The EPR spectra of the members of the series Pr0.5RE0.5Ba2Cu3O6+x (RE = Pr, La, Nd, Sm, Eu, Gd, Dy, Ho, Y, Er, Tm, Yb, and Lu) in the orthorhombic phase are investigated at low temperature. The EPR spectra arise from two different paramagnetic centers, one from divalent copper ions in orthorhombic local crystal field symmetry and another from exchange coupled pairs of copper ions whose origin is discussed. The EPR spectra essentially depend on the time exposition. The EPR spectra of some divalent and trivalent rare earth ions are recorded. The crystal field analysis is done for the trivalent ytterbium ions. The semiconducting behaviour of the dc conductivity can be attributed to thermally activated small polaron hopping motion. Copyright © 1994 WILEY‐VCH Verlag GmbH & Co. KGaA

Oxygenated and non‐oxygenated LaBaSrCu3O6+x ceramics in the tetragonal phase are studied using X‐ray, EPR, and magnetic measurements. A Meissner signal for the oxygenated sample corresponding to almost perfect diamagnetism is measured below 35 K. However, EPR data indicate that at least some parts of the sample become superconducting already below 62 K. Magnetic susceptibility of the non‐oxygenated sample exhibit a significant paramagnetic contribution attributed to Cu(1) ions ferromagneticall coupled to the Cu(2) planes. Copyright © 1993 WILEY‐VCH Verlag GmbH & Co. KGaA

Temperature dependence of the b2(0) spin-hamiltonian parameter for Gd3+ in RbCdF3 single crystals is described. The dependence is interpreted in terms of the 4f7 electrons coupling to the whole phonon spectrum of the crystal. The presented data give also an insight into the dynamics of charge compensators causing a tetragonal distortion of the crystal field.

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Temperature dependence of the second-order spin-lattice coefficients for PbF2:Gd3+ is reported. It is shown that the thermal expansion of the crystal lattice contributes only in about 14% to the observed dependence and the rest should be ascribed to a dynamic coupling between the 4f7 electrons and lattice vibrations. The results are parametrized in both the Einstein and the Debye models and it is shown that the phenomenological parameters obtained from such parametrization can be made to coincide in both models if a specific value of the Einstein frequency omega-E is properly chosen. Both models of parameterization show that the GAMMA-3g vibrating mode couples to the 4f7 electrons much weaker than the GAMMA-5g one.