Relationship between Superconductivity and Antiferromagnetism in LaFe(As^sub 1-x^P^sub x^)O Revealed by ^sup 31^P-NMR

We performed 31P-NMR measurements on LaFe(...)O to investigate the relationship between antiferromagnetism and superconductivity. The antiferromagnetic (AFM) ordering temperature TN and the moment ...ord are continuously suppressed with increasing P content x and disappear at x = 0.3 where bulk superconductivity appears. At this superconducting x = 0.3, quantum critical AFM fluctuations are observed, indicative of the intimate relationship between superconductivity and low-energy AFM fluctuations associated with the quantum-critical point in ... The relationship is similar to those observed in other isovalent-substitution systems, e.g., ... and ..., with the "122" structure. Moreover, the AFM order reappears with further P substitution (x > 0.4). The variation of the ground state with respect to the P substitution is considered to be linked to the change in the band character of Fe-3d orbitals around the Fermi level. (ProQuest: ... denotes formulae/symbols omitted.)