Electron-spin-lattice relaxation in GdBa{sub 2}Cu{sub 3}O{sub 6+{ital x}}
- Institute of Radio Engineering and Electronics, Russian Academy of Sciences, 103907 Moscow (Russian Federation)
A method of directly measuring electron-spin-lattice relaxation times {ital T}{sub 1} as short as 10{sup {minus}9}--10{sup {minus}10} s is developed. The technique is based on the relation between the EPR absorption magnitude and the response of longitudinal spin magnetization to a radio-frequency modulation of microwave power. By means of this method, the electron-spin-lattice relaxation of Gd{sup 3+} ions was studied in high-{ital T}{sub {ital c}} superconductor GdBa{sub 2}Cu{sub 3}O{sub 6+{ital x}} at 0.4{le}{ital x}{le}0.84 in the temperature range 77--300 K. It was found that spin-spin interactions between Gd{sup 3+} ions have no influence on the {ital T}{sub 1} value, so Gd{sup 3+} can be used as a spin probe even in concentrated substances. The relaxation rate {ital W}=({ital TT}{sub 1}){sup {minus}1} is shown to consist of two parts, {ital W}{sub 0} and {ital W}{sub AF}, resulting from the quasiparticle contribution and the antiferromagnetic fluctuations, respectively. Both contributions reveal a spin gap opening with {Delta}/{ital k}{sub {ital B}}=200 K. The temperature variation of {ital W}{sub 0} is in agreement with published {sup 89}Y NMR data in YB{sub 2}Cu{sub 3}O{sub 6+{ital x}}, the {ital W}{sub 0} values being proportional to the {sup 89}Y Knight shifts. The ratio {ital W}{sub AF}/{ital W}{sub 0} shows Curie-Weiss behavior and increases strongly as {ital x} decreases. This implies incomplete filtering of the antiferromagnetic fluctuations over the finite-sized Gd{sup 3+} 4{ital f} orbitals and symmetry breaking due to oxygen vacancies.
- OSTI ID:
- 78679
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 52, Issue 2; Other Information: PBD: 1 Jul 1995
- Country of Publication:
- United States
- Language:
- English
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