Crossover between magnetism and superconductivity in low H-doped LaFeAsO

TL;DR

This study investigates the phase diagram of hydrogen-doped LaFeAsO, revealing a crossover region where magnetism and superconductivity coexist, similar to other rare-earth-1111 pnictides, using multiple experimental techniques.

Contribution

It provides the first systematic analysis of H-doped LaFeAsO's phase diagram, highlighting the crossover between magnetism and superconductivity and its similarity to other 1111 families.

Findings

Long-range SDW order at x=0.01 with T_n=119 K

SDW order at 38 K for x=0.05 coexisting with superconductivity below 10 K

Presence of a crossover region between magnetism and superconductivity

Abstract

By a systematic study of the hydrogen-doped LaFeAsO system by means of dc resistivity, dc magnetometry, and muon-spin spectroscopy we addressed the question of universality of the phase diagram of rare-earth-1111 pnictides. In many respects, the behaviour of LaFeAsO_(1-x)H_(x) resembles that of its widely studied F-doped counterpart, with H^- realizing a similar (or better) electron-doping in the LaO planes. In a x = 0.01 sample we found a long-range SDW order with T_n = 119 K, while at x = 0.05 the SDW establishes only at 38 K and, below T_c = 10 K, it coexists at a nanoscopic scale with bulk superconductivity. Unlike the abrupt M-SC transition found in the parent La-1111 compound, the presence a crossover region makes the H-doped system qualitatively similar to other Sm-, Ce-, or Nd-1111 families.