Sustained phase separation and spin glass in Co-doped K$_{x}$Fe$_{2-y}$Se$_{2}$ single crystals

Hyejin Ryu; Kefeng Wang; M. Opacic; N. Lazarevic; J. B. Warren; Z. V. Popovic; E. S. Bozin; C. Petrovic

doi:10.1103/PhysRevB.92.174522

paper

Sustained phase separation and spin glass in Co-doped K $_{x}$ Fe $_{2 - y}$ Se $_{2}$ single crystals

arXiv:1604.03545 · doi:10.1103/PhysRevB.92.174522

Abstract

We present Co substitution effects in K $_{x}$ Fe $_{2 - y - z}$ Co $_{z}$ Se $_{2}$ (0.06 $\leq$ $z$ $\leq$ 1.73) single crystal alloys. By 3.5\% of Co doping superconductivity is suppressed whereas phase separation of semiconducting K $_{2}$ Fe $_{4}$ Se $_{5}$ and superconducting/metallic K $_{x}$ Fe $_{2}$ Se $_{2}$ is still present. We show that the arrangement and distribution of superconducting phase (stripe phase) is connected with the arrangement of K, Fe and Co atoms. Semiconducting spin glass is found in proximity to superconducting state, persisting for large Co concentrations. At high Co concentrations ferromagnetic metallic state emerges above the spin glass. This is coincident with changes of the unit cell, arrangement and connectivity of stripe conducting phase.

7 pages, 6 figures

Sustained phase separation and spin glass in Co-doped Kx​Fe2−y​Se2​ single crystals

Abstract

Sustained phase separation and spin glass in Co-doped K $_{x}$ Fe $_{2 - y}$ Se $_{2}$ single crystals