Magnetic structure of quasi-one-dimensional antiferromagnetic TaFe${}_{1+y}$Te${}_3$

We report the magnetic structure of TaFe${}_{1+y}$Te${}_3$ single crystals by means of neutron diffraction measurements. TaFe${}_{1+y}$Te${}_3$ possesses a layered structure with a formation of two-leg zigzag ladders along the $b$ axis. We find that TaFe${}_{1+y}$Te${}_3$ undergoes an antiferromagnetic transition at 178 K with Fe1 spins of the intraladders ferromagnetically aligned and with Fe1 spins of the interladders antiferromagnetically coupled. Furthermore, spins of the neighboring interstitial Fe2 ($y$) ions align parallel to the Fe1 spins of each ladder. These findings are distinct from the magnetic structure of the recently discovered spin-ladder compound BaFe${}_2$Se${}_3$. TaFe${}_{1+y}$Te${}_3$ may serve as a model system for investigating the interesting physics of quasi-one-dimensional ferromagnetic systems.

Figure 1

Schematics of the (a) monoclinic crystal structure and (b) spin structure, and (c) detailed view of the zigzag ladders of TaFe${}_{1+y}$Te${}_3$. Fe1 sites are fully occupied, while Fe2 sites represented by a different symbol are only partially occupied. The inset in (b) shows the OOP direction, ${[10-1]}_{\mathrm{rec}}$ in reciprocal space, which is perpendicular to the cleaved plane and tilts from the ${[10-1]}_{\mathrm{r}}$ direction in real space (i.e., the moment direction) by 17.6°. The pink dashed lines in (c) illustrate two nearest-neighboring Fe1 chains forming a zigzag ladder.

Figure 2

Temperature dependence of (a) magnetization and (b) resistivity of TaFe${}_{1+y}$Te${}_3$ along both IP and OOP directions. The exact IP directions measured are not specified.

Figure 3

(a) Rocking curve of magnetic reflections (−0.5 0 0.5) and (0.5 0 0.5) at $T$ $=$ 5 K. (b) Temperature dependence of (0.5 0 0.5) magnetic peak intensity. Solid curves are Gaussian fits.

Figure 4

Plots of the comparison of observed and calculated intensities of various (a) nuclear and (b) magnetic diffraction peaks, showing the quality of data refinement. Red lines are visual guides.