Experimentally probing the intrinsic properties of superconductors—such as the London penetration depth λ and the critical fields Hc1 and Hc2—poses a difficult task. Various sample- and measurement-related factors can impact the efficacy of results obtained for λ or Hc1, such as perturbations to the magnetic properties of a superconducting sample or crystalline defects. One measurement technique that can minimize the impact of both of these issues is known as Nitrogen Vacancy (NV) center magnetometry. In this work, we use NV center magnetometry to perform minimally-invasive measurements of the lower critical field Hc1 and the London penetration depth λ on a sample of Ba(Fe1−xCox)2As2, x = 7.4% (BaCo122).

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