Se*

The family of compounds of general formula Li_1-xFe_x(OH)Fe_1-ySe, consisting of alternating Fe_1-ySe and Li_1-xFe_x(OH) layers, have been found to superconduct with T_c’s of ≈ 40 K. The hydroxide layer, containing roughly 20 % substitution of Li for Fe, has been shown to display magnetism well below the superconducting transition in the region of 10 K. This has been alternately reported as an ordering of the hydroxide layer Fe moments ferromagnetically and antiferromagnetically. Our study elucidates this magnetism by taking advantage of the flexible synthesis of these compounds allowing investigation of superconducting and non-superconducting variants in an effort to disentangle magnetism form superconductivity. Utilizing static and dynamic magnetometry, measurement of heat capacity and muon spin relaxation we propose the magnetism of the hydroxide layer to be glass-like and coexist with superconductivity.

PRB, 95, 134419 (2017)