Inter- to intra-layer resistivity anisotropy of NdFeAs(O,H) with various hydrogen concentrations
Abstract
With molecular beam epitaxy and a topotactic chemical reaction, we prepared NdFeAs(O,H) epitaxial thin films with various hydrogen concentrations on 5° vicinal-cut MgO substrates. By measuring the resistivities along the longitudinal and transversal directions, the a b -plane and the c -axis resistivities (ρa b and ρc) were obtained. The resistivity anisotropy γρ≡ρc/ρa b of NdFeAs(O,H) with various hydrogen concentrations was compared with that of NdFeAs(O,F). At the H concentrations which led to superconducting transition temperatures Tc over 40 K, γρ recorded ∼100 -150 at 50 K. On the other hand, a low γρ value of 9 was observed with the highest-doped sample. The exponent β of the a b -plane resistivity obtained by fitting a power-law expression ρa b(T ) =ρ0+A Tβ to the data was close to unity down to a low temperature in the vicinity where the second antiferromagnetic phase locates, which may be related to the quantum critical point discussed at the overdoped side of the phase diagram.
- Publication:
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Physical Review Materials
- Pub Date:
- May 2022
- DOI:
- 10.1103/PhysRevMaterials.6.054802
- arXiv:
- arXiv:2204.01554
- Bibcode:
- 2022PhRvM...6e4802C
- Keywords:
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- Condensed Matter - Superconductivity
- E-Print:
- Appeared in Physical. Rev. Materials