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Antiferromagnetic Alignment and Relaxation Rate of Gd Spins in the High Temperature Superconductor GdBa_2Cu_3O_(7-delta)

R. J. Ormeno·C. E. Gough·G. Yang
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Abstract

The complex surface impedance of a number of GdBa$_2$Cu$_3$O$_{7-δ}$ single crystals has been measured at 10, 15 and 21 GHz using a cavity perturbation technique. At low temperatures a marked increase in the effective penetration depth and surface resistance is observed associated with the paramagnetic and antiferromagnetic alignment of the Gd spins. The effective penetration depth has a sharp change in slope at the Néel temperature, $T_N$, and the surface resistance peaks at a frequency dependent temperature below 3K. The observed temperature and frequency dependence can be described by a model which assumes a negligibly small interaction between the Gd spins and the electrons in the superconducting state, with a frequency dependent magnetic susceptibility and a Gd spin relaxation time $τ_s $ being a strong function of temperature. Above $T_N$, $τ_s$ has a component varying as $1 / (T - T_N)$, while below $T_N$ it increases $\sim T^{-5}$.

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R. J. Ormeno, C. E. Gough, G. Yang. 2000-01-26. Antiferromagnetic Alignment and Relaxation Rate of Gd Spins in the High Temperature Superconductor GdBa_2Cu_3O_(7-delta). https://doi.org/10.1103/physrevb.63.104517

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