Magnetic structure of the quasi-one-dimensional $\mathrm{L}{\mathrm{a}}_3\mathrm{Os}{\mathrm{O}}_7$ as determined by neutron powder diffraction

Insulating $5d^3\mathrm{L}{\mathrm{a}}_3\mathrm{Os}{\mathrm{O}}_7$ and the isostructural hole-doped analog $\mathrm{L}{\mathrm{a}}_{2.8}\mathrm{C}{\mathrm{a}}_{0.2}\mathrm{Os}{\mathrm{O}}_7$ that feature pseudo-one-dimensional zigzag chains of corner-sharing $\mathrm{Os}{\mathrm{O}}_6$ octahedra have been synthesized and their magnetic and electrical transport properties characterized. Both compounds are insulating antiferromagnets. Long range magnetic order between the antiferromagnetic chains is determined with a propagation vector $k=1/2,1/2,1$ and $T_{\mathrm{N}}=45$ and 33 K for the parent and doped materials. An $\mathrm{O}{\mathrm{s}}^{5+}$ moment of $1.7\left(1\right){\mu }_B$ for $\mathrm{L}{\mathrm{a}}_3\mathrm{Os}{\mathrm{O}}_7$ and $1.2\left(2\right){\mu }_B$ for $\mathrm{L}{\mathrm{a}}_{2.8}\mathrm{C}{\mathrm{a}}_{0.2}\mathrm{Os}{\mathrm{O}}_7$ is refined. The long range magnetic structure is compared to the isostructural compounds $\mathrm{L}{\mathrm{a}}_3\mathrm{Ru}{\mathrm{O}}_7$ and $\mathrm{L}{\mathrm{a}}_3\mathrm{Mo}{\mathrm{O}}_7$, both of which adopt different magnetic structures.

Figure 1

Crystal structure of $\mathrm{L}{\mathrm{a}}_3\mathrm{Os}{\mathrm{O}}_7$ shown with views (a) down the $b$ axis and (b) down the $c$-axis. Os cations are shown as blue spheres within the blue octahedra, La cations are shown as gray spheres, and O anions are shown as red spheres.

Figure 2

Refined neutron powder diffraction data for $\mathrm{L}{\mathrm{a}}_3\mathrm{Os}{\mathrm{O}}_7$ at 300 K. Black symbols, red curves, and blue curves represent the observed data, calculated pattern, and difference, respectively. The upper and lower sets of hash marks signify the main phase and excess $\mathrm{L}{\mathrm{a}}_2{\mathrm{O}}_3$ impurity, respectively.

Figure 3

The temperature dependence of the electrical resistivity of $\mathrm{L}{\mathrm{a}}_3\mathrm{Os}{\mathrm{O}}_7$ (black) and $\mathrm{L}{\mathrm{a}}_{2.8}\mathrm{C}{\mathrm{a}}_{0.2}\mathrm{Os}{\mathrm{O}}_7$ (red). The inset shows the linear relationship on a $T^{-1/2}$ scale as described in the text.

Figure 4

The temperature dependence of the magnetization of (a) $\mathrm{L}{\mathrm{a}}_3\mathrm{Os}{\mathrm{O}}_7$ and (b) $\mathrm{L}{\mathrm{a}}_{2.8}\mathrm{C}{\mathrm{a}}_{0.2}\mathrm{Os}{\mathrm{O}}_7$. The inverse relationship with Curie-Weiss fits (red lines) are shown in (c).

Figure 5

High $d$-spacing neutron powder diffraction data showing the reflections arising due to magnetic scattering from $\mathrm{L}{\mathrm{a}}_3\mathrm{Os}{\mathrm{O}}_7$. The calculated pattern including the magnetic model at 5 K is shown as the red curve.

Figure 6

Magnetic structure of $\mathrm{L}{\mathrm{a}}_3\mathrm{Os}{\mathrm{O}}_7$ determined by analysis of neutron powder diffraction data shown on a $2\times 2\times 1$ cell. The spins are coupled antiferromagnetically along each corner connected 1D chain of $\mathrm{O}{\mathrm{s}}^{5+}$ octahedra down the $c$ axis.