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Pinning forces and lower critical fields in YBa sub 2 Cu sub 3 O sub y crystals: Temperature dependence and anisotropy

Journal Article · · Physical Review Letters; (USA)
;  [1]
  1. Department of Physics, Northeastern University, Boston, MA (USA)
Measurements of the field-dependent radiofrequency penetration depth {lambda}({ital H},{ital T}) are used to delineate the lower-critical-field {ital H}{sub {ital c}1}-{ital T} phase boundary, and to study flux dynamics in YBa{sub 2}Cu{sub 3}O{sub {ital y}} crystals. For both {bold H}{parallel}{bold {cflx c}} and {bold H}{perpendicular}{bold {cflx c}} {ital H}{sub {ital c}1} obeys a BCS temperature dependence with a temperature-independent anisotropy of 3.4{plus minus}0.3. In the mixed state, the data obey {lambda}{sup 2}({ital H})=({phi}{sub 0}/{mu}{sub 0}{alpha}({ital T})){ital B}({ital H}), and yield both the functional dependence {ital B}({ital H}) and the pinning force constant {alpha}({ital T}). The latter is anisotropic, obeys an approximately (1{minus}{ital t}{sup 2}){sup 2} temperature dependence, and vanishes slightly below the bulk transition temperature.
OSTI ID:
6084909
Journal Information:
Physical Review Letters; (USA), Journal Name: Physical Review Letters; (USA) Vol. 65:16; ISSN PRLTA; ISSN 0031-9007
Country of Publication:
United States
Language:
English