Spin-Lattice Relaxation Effects in Critical Sound Propagation |
| A. Pawlak Institute of Physics, A. Mickiewicz University, Matejki 48/49, 60-769 Poznań, Poland |
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| The nonasymptotic critical properties of sound propagation are studied in compressible Ising system above TC. In the present paper we analyse a model where in addition to the coupling to two order-parameter fluctuations the sound mode couples linearly to the fluctuations of spin-energy and lattice-energy densities. Both subsystems exchange energy with the rate determined by the bare spin-lattice relaxation time. The total energy may be conserved or not. The crossover between insulator-like behaviour ~t-2α and metal-like behaviour ~t-(zν+α) in ultrasonic attenuation is investigated according to the value of ultrasonic frequency, the reduced temperature t, bare relaxation times and various coupling constants. |
| DOI: 10.12693/APhysPolA.92.449 PACS numbers: 05.70.Jk, 62.65.+k |