Regensburg 2000 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 23: Elektronenstruktur in HTSL

TT 23.9: Vortrag

Freitag, 31. März 2000, 11:45–12:00, H18

Cu spin dynamics in doped La₂CuO₄ as revealed by ESR — •V. Kataev^1,2, A. Validov², B. Büchner¹, M. Hücker¹, and H. Berg¹ — ¹II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln — ²Kazan Institute for Technical Physics, RAS, 420029 Kazan, Russia

Electron spin resonance (ESR) measurements of Gd spin probes in La_2−x−yEu_ySr_xCuO₄ reveal drastic changes of the Cu spin dynamics due to the structural transition to the low temperature tetragonal (LTT) phase which is induced by Eu substitution for La. At small hole contents (0< x≤ 0.02) a strong enhancement of magnetic fluctuations on the ESR frequency scale is observed in the antiferromagnetically ordered LTT phase. At larger hole doping (0.08≤ x ≤ 0.17) the Cu spin fluctuation frequency ω_sf in the LTT phase considerably decreases with decreasing temperature. This slowing down of ω_sf is particulary pronounced for x∼ 1/8 and is found to compete with bulk superconductivity. The results are discussed in relation to stripe correlations of spins and charges in the cuprates. The data for intermediate hole content are consistent with the stripe model and suggest a glassy character of the stripe order in the LTT phase. On the other hand, no evidence for the stripe phase formation at small hole concentrations is found.

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