CONDENSED MATTER

Spin dynamics and structural phase transitions in quasi-2D antiferromagnets R$_2$CuO$_4$ (R${}={}$Pr, Sm, and Eu)

E. I. Golovenchits, V. A. Sanina

Ioffe Physico-Technical Institute, Russian Academy of Sciences, St. Petersburg

Abstract: Spin and lattice dynamics of R$_2$CuO$_4$ (R${}={}$Pr, Sm, and Eu) crystals were studied over the frequency and temperature ranges $20$–$250$ GHz and $5$–$350$ K, respectively. The absorption coefficients of the R$_2$CuO$_4$ crystals (R${}={}$Pr, Sm, and Eu) were found to change dramatically at temperatures of, respectively, $20$, $80$, and $150$ K over a broad frequency range above $120$ GHz. The absorption jumps were caused by the structural phase transitions. Broad spin-wave bands were observed in the high-temperature phases of all crystals studied. Absorption lines due to lattice dynamics were observed near the temperatures of structural phase transition over a broad frequency range, including the frequencies corresponding to the spin-wave bands.

PACS: 64.60.Ht, 75.30.Ds, 76.50.+g

Received: 24.05.2001

 English version: Journal of Experimental and Theoretical Physics Letters, 2001, 74:1, 20–23

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