Field-induced structural transition and irreversible domain detwinning in the antiferromagnet ${\mathrm{Fe}}_{1.1}\mathrm{Te}$

Single-crystal x-ray diffraction in pulsed magnetic fields of up to 31 T was used to investigate the iron telluride antiferromagnet ${\mathrm{Fe}}_{1.1}\mathrm{Te}$, which is a parent of the Fe-based chalcogenide superconductors. At temperatures below the Néel temperature $T_N\simeq 60$ K, high magnetic fields perpendicular to the $c$ axis lead to an irreversible detwinning of the crystal at the field $H_R$, where magnetocrystalline domains are selected by a moment reorientation process. Just below $T_N$, the onset of a structural transition at the critical field $H_C>H_R$, which delimits the antiferromagnet phase, indicates a partial restoration of the high-temperature tetragonal symmetry. The lattice and magnetic answers to an in-plane magnetic field are discussed, emphasizing the strength of magnetoelastic coupling in ${\mathrm{Fe}}_{1.1}\mathrm{Te}$.

Figure 1

Temperature dependence of the diffracted intensity of $\left(404\right), \left(40\overline{4}\right)$, and $\left(044\right)$ Bragg reflections. The splitting due to the monoclinic distortion is clearly observed at $T_N=58$ K.

Figure 2

Time dependence of the diffracted intensity of the $\left(404\right), \left(40\overline{4}\right)$, and $\left(044\right)$ Bragg reflections at the temperatures $T=$ (a) 73 K, (b) 55 K, (c) 32 K, and (d) 13 K during a 31 T magnetic field pulse. Results presented here are integrated over the full range of $\gamma$ angle (out-of-diffraction plane component) $\mathrm{\Delta }\gamma =\pm 0.5^{\circ }$ and were obtained in a single magnetic field pulse. Top: Trace of a 31 T magnetic-field pulse and drawing of the scattering geometry showing the direction of the applied magnetic field and the crystal axes in the high temperature tetragonal phase.

Figure 3

Field dependence of the diffracted intensity of the $\left(404\right), \left(40\overline{4}\right)$, and $\left(044\right)$ Bragg reflections at the temperatures $T=$ (a) 73 K, (b) 55 K, (c) 32 K, and (d) 13 K. (e) Field dependence of the magnetization up to 30 T at $T=30$ K. (f) Temperature dependence of the magnetic susceptibility, where $\langle \chi \rangle$ and ${\chi }_a$ are estimated from the rise and fall, respectively, of pulsed-field measurements, and where ${\chi }_b$ is estimated assuming a half-half repartition of the domains.

Figure 4

Magnetic-field-temperature phase diagram of ${\mathrm{Fe}}_{1.1}\mathrm{Te}$ with $\mathbf{H}\perp \mathbf{c}$. Closed symbols: Critical fields extracted from x-ray diffraction in field up to 31 T. Open symbols: Critical fields from magnetization measurements from Ref. [28].