Competition between orthorhombic and re-entrant tetragonal phases in underdoped Ba$_{1 − x}$K$_x$Fe$_2$As$_2$ probed by the response to controlled disorder
Résumé
Low-temperature (22 K) irradiation with 2.5-MeV electrons, creating point defects affecting elastic scattering, was used to study the competition between stripe C$_2$ and tetragonal C$_4$ antiferromagnetic phases which exist in a narrow doping range around x = 0.25 in hole-doped Ba$_{1− x}$K$_x$Fe$_2$As$_2$. In nearby compositions outside of this range, at x = 0.22 and x = 0.19, the temperatures of both the concomitant orthorhombic/stripe antiferromagnetic transition $T_{C2}$ and the superconducting transition $T_c$ are monotonically suppressed by added disorder at similar rates of about 0.1 K/μ$\Omega$ cm, as revealed through using resistivity variation as an intrinsic measure of scattering rate. In a stark contrast, a rapid suppression of the C$_4$ phase at the rate of 0.24 K/μ$\Omega$cm is found at x = 0.25. Moreover, this suppression of the C$_4$ phase is accompanied by unusual disorder-induced stabilization of the C$_2$ phase, determined by resistivity and specific heat measurements. The rate of the C$_4$ phase suppression is notably higher than the suppression rate of the spin-vortex phase in the Ni-doped CaKFe$_4$As$_4$ (0.16 K/μ$\Omega$ cm).
Origine : Fichiers éditeurs autorisés sur une archive ouverte