Collinear order in a frustrated three-dimensional spin-$\frac{1}{2}$ antiferromagnet Li${}_2$CuW${}_2$O${}_8$

Abstract

Magnetic frustration in three dimensions (3D) manifests itself in the spin-$\frac{1}{2}$ insulator Li${}_2$CuW${}_2$O${}_8$. Density-functional band-structure calculations reveal a peculiar spin lattice built of triangular planes with frustrated interplane couplings. The saturation field of 29 T contrasts with the susceptibility maximum at 8.5 K and a relatively low Néel temperature $T_N\simeq 3.9$ K. Magnetic order below $T_N$ is collinear with the propagation vector $(0,\frac{1}{2},0)$ and an ordered moment of 0.65(4) $\hat{I}{¼}_B$ according to neutron diffraction data. This reduced ordered moment together with the low maximum of the magnetic specific heat ($C^{\max }/R\simeq 0.35$) pinpoint strong magnetic frustration in 3D. Collinear magnetic order suggests that quantum fluctuations play crucial role in this system, where a non-collinear spiral state would be stabilized classically.

published version with supplemental material merged into the text