Magnetic levitation force and penetration depth in type-II superconductors
- Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, Texas 77204 (United States)
The superconducting levitation force [ital F] acting on a magnet placed above a type-II superconductor in both Meissner and mixed states is calculated as a function of temperature, based upon the London model. A simple relationship between the levitation force and the London penetration depth [lambda] is found. In particular, in the limit of [ital a]/[lambda][much gt]1, where [ital a] is the separation between the magnet and the superconductor, [ital F] varies linearly with [lambda], regardless of the shape of the magnet. The temperature dependences of [lambda] and [ital F] are examined for various superconducting pairing states, including [ital s]-wave, [ital d]-wave, and [ital s]+[ital id] states. It is found that, at low temperatures, both [lambda] and [ital F] show an exponential temperature dependence for [ital s]-wave, linear-[ital T] for [ital d]-wave, and [ital T][sup 2] dependence in a wide low-temperature range for the [ital s]+[ital id] state with a dominant [ital d]-wave component. The magnetic force microscope (MFM) is proposed to accurately measure the temperature-dependent levitation force. It is shown that the microscopic size of the MFM tip enables one to obtain the intrinsic temperature-dependent penetration depth of a single grain, in spite of the overall quality of the superconducting sample.
- OSTI ID:
- 7060950
- Journal Information:
- Physical Review, B: Condensed Matter; (United States), Vol. 51:1; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
TYPE-II SUPERCONDUCTORS
MAGNETIC PROPERTIES
D STATES
LONDON EQUATION
MIXED STATE
PENETRATION DEPTH
S STATES
TEMPERATURE DEPENDENCE
ENERGY LEVELS
EQUATIONS
PHYSICAL PROPERTIES
SUPERCONDUCTORS
665411* - Basic Superconductivity Studies- (1992-)