Unexpected ($\pi,\pi$) order in Fe$_{1.1}$Te
ORAL
Abstract
We have studied the evolution of the magnetic and crystal structure in single crystalline Fe$_{1.1}$Te, an iron-rich parent of the chalcogenide superconductor family. While a structural transition to a monoclinic symmetry occurs at $\sim 60$ K, magnetic peaks at $2\pi \cdot (0.48, 0)$ only arise below T$_{N}\approx 58$ K, and can be understood as bicollinear magnetism with discommensuration defects. \footnote{I. Zaliznyak \textit{et al.}, Phys. Rev. B \textbf{85}, 085105 (2012)} Unexpectedly, we have also observed resolution limited peaks at approximately $(\pi, \pi)$, arising at the same temperature T$_{N}$, and exhibiting temperature hysteresis similar to that seen in magnetic susceptibility, perhaps indicating that these peaks are of magnetic origin. Additionally, the position of these peaks is nearly the same as in the parent compounds of the iron pnictide family of superconductors, where magnetic order is simple collinear commensurate antiferromagnetism. The origin of these new peaks near ($\pi, \pi$) and their relationship to the dominant bicollinear magnetic order observed in Fe$_{1.1}$Te presents a puzzle.
*Work at BNL supported by Office of Basic Energy Sciences, US DOE, under Contract No. DE-AC02-98CH10886. We acknowledge the support of NIST, US Department of Commerce, in providing the neutron research facilities used in this work.
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