Dipole energy dissipation and nuclear spin diffusion in mixed-state superconducting vanadium
The decay of nuclear spin-spin energy has been studied in the mixed state of vanadium and anomalously rapid relaxation rates are found as compared to the rates for spin-lattice relaxation of Zeeman energy. The experiment was performed by adiabatically demagnetizing the spins in the rotating frame at a field larger than H/subc/$sub 2$ and then cycling the field to bring the sample into the mixed state for a variable time. The residual dipolar energy is detected, once the field is raised, by adiabatically remagnetizing the sample on resonance. I show that the relaxation observed, after the vortices are pinned, is due to a cross relaxation of a spin energy associated with the magnetic field gradients in the mixed state and the dipolar energy which is in semiequilibrium with the quadrupole energy. This process is mediated by a current of magnetization, proportional to the diffusion coefficient D, which is driven by the field gradients and uses dipolar energy as a heat sink. Using a field distribution in the mixed state calculated by Marcus, I find D = 2.8 +- 0.9 x 10$sup -12$ cm$sup 2$ sec$sup -1$ from the measurements of the relaxation rate of dipolar energy and of the quadrupole system heat capacity. This measurement of D is the first for a metal or for nuclei with I > 1/2 and is twice the value predicted by the moment-moment calculation of Redfield and Yu. In the presence of large field gradien-ts, dynamic quenching of the diffusion is observed. (AIP)
- Research Organization:
- IBM Thomas J. Watson Research Center, Yorktown Heights, New York New York 10598
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-33-020784
- OSTI ID:
- 4081617
- Journal Information:
- Phys. Rev., B, v. 13, no. 1, pp. 68-80, Other Information: Orig. Receipt Date: 30-JUN-76
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
Ceramics
& Other Materials-Metals & Alloys-Properties
Structure & Phase Studies
N66200 -Physics (Low Temperature)-Superconductivity
360104* -Materials-Metals & Alloys-Physical Properties
*VANADIUM- SPIN-SPIN RELAXATION
DIFFUSION
NUCLEAR MAGNETIC RESONANCE
RELAXATION
SPIN-LATTICE RELAXATION
SUPERCONDUCTORS