Effect of Co and Ni substitution on the two magnetostructural phase transitions inFe1.12Te

Abstract

Here we present the results of high-resolution x-ray diffraction experiments along with specific heat, resistivity, and magnetization measurements of chemically well-characterized ${\mathrm{Fe}}_{1.12\ensuremath{-}x}{M}_{x}\mathrm{Te}$ ($M=\mathrm{Co}$, Ni) samples. The motivation is to investigate how the two coupled magnetostructural phase transitions in the antiferromagnetic parent compound ${\mathrm{Fe}}_{1.12}\mathrm{Te}$ of chalcogenide superconductors can be tuned. While the two-step magnetostructural transition (tetragonal-to-orthorhombic followed by orthorhombic-to-monoclinic) persists in ${\mathrm{Fe}}_{1.10}{\mathrm{Co}}_{0.02}\mathrm{Te}$, only one, tetragonal-to-orthorhombic transition was observed in ${\mathrm{Fe}}_{1.10}{\mathrm{Ni}}_{0.02}\mathrm{Te}$. Upon increasing the Co and Ni substitution, the structural phase transitions and the long-range magnetic order are systematically suppressed without any sign of superconductivity. For high substitution levels $(x\ensuremath{\ge}0.05)$, a spin-glass-like behavior was observed and the low-temperature structure remains tetragonal. From our results, it can be inferred that the electron doping strongly suppresses the magnetostructural phase transitions.