The imaginary part of the phonon polarization operator and the renormalization of the sound velocity due to the spin-phonon interaction are calculated in a cubic ferrodielectric for large atomic spins in the spin-wave temperature region.
Diffusion in Crystals with Competing Interactions of Migrating IonsBY V. ZUBKUS (a), P. KUNDROTAS (b), S. LAPINSKAS (b), and V. KASHCHEEV t (c) Transport processes are investigated by means of the lattice gas model with nearest and nextnearest neighbour attractive and repulsive interactions. The temperature and concentration dependences of self-diffusion coefficient and electroconductivity in the disordered homogeneous phase of these systems are calculated by the cluster approximation. The regions of deviation from the Arrhenius law are determined. The spatial-time distributions of migrating particles are obtained. The influence of strong short-range interactions on the relaxation time of the diffusion process is investigated. Several experimental results of diffusion in systems with strong shortrange correlations are discussed by the theory proposed.Die Transportprozesse in Kristallen vom KDP-Typ werden im Rahmen eines Gittergasmodells beschrieben. AbstoBende und anziehende Wechselwirkungen zwischen niichsten und uberniichsten Ionen der Gitterpunkte werden in Betracht gezogen. Die Temperatur-und Konzentrationsabhangigkeiten der Selbstdiffusions-und Leitfilhigkeitskoeffizienten der ungeordneten homogenen Phase, dieser Systeme werden mit der Methode der Clusterniiherung berechnet. I n diesen Kristallen werden Bereiche gefunden, die Abweichungen vom Arrhenius Gesetz aufweisen. Die zeitliche und riiumliche Teilchenverteilungen werden fur diese Systeme bestimmt. Der EinfluB einer Nahordnung auf die Relaxationszeit des Diffusionsprozesses wird behandelt. Die experimentellen Diffusionsergebnisse werden im Rahmen der entwickelten Theorie analysiert. l ) SU-232OOO Vilnius, USSR. 2, Sauletekio al. 9, SU-232054 Vilnius, USSR. 8, SU-229021 Riga-Salaspils, USSR.
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