期刊
PHYSICAL REVIEW B
卷 85, 期 22, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.85.224518
关键词
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资金
- US Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering [DE-AC02-76SF00515]
- NSF [PHY-0425897]
- DARPA COMPASS grant
Scanning SQUID susceptometry images the local magnetization and susceptibility of a sample. By accurately modeling the SQUID signal we can determine physical properties such as the penetration depth and permeability of superconducting samples. We calculate the scanning SQUID susceptometry signal for a superconducting slab of arbitrary thickness with isotropic London penetration depth lambda on a nonsuperconducting substrate, where both slab and substrate can have a paramagnetic response that is linear in the applied field. We derive analytical approximations to our general expression in a number of limits. Using our results, we fit experimental susceptibility data as a function of the sample-sensor spacing for three samples: (1) delta-doped SrTiO3, which has a predominantly diamagnetic response, (2) a thin film of LaNiO3, which has a predominantly paramagnetic response, and (3) the two-dimensional electron layer at a SrTiO3/LaAlO3 interface, which exhibits both types of response. These formulas will allow the determination of the concentrations of paramagnetic spins and superconducting carriers from fits to scanning SQUID susceptibility measurements.
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