Ground-state properties of the double trillium lattice antiferromagnet KBaCr${}_2$(PO${}_4$)${}_3$

Abstract

Trillium lattices formed by corner-shared triangular units are the platform for magnetic frustration in three dimensions. Herein, we report structural and magnetic properties of the Cr-based double trillium lattice material KBaCr${}_2$(PO${}_4$)${}_3$ studied by x-ray diffraction, magnetization, heat capacity, thermal conductivity, and ${}^{31}$P nuclear magnetic resonance (NMR) measurements complemented by density-functional band-structure calculations. Heat capacity and ${}^{31}$P NMR measurements reveal the magnetic transition at $T_{N1}\simeq 13.5$ K in zero field followed by another transition at $T_{N2}\simeq 7$ K in weak applied fields. The NMR sublattice magnetization confirms that the transition at $T_{N1}$ is 3D in nature. The ${}^{31}$P spin-lattice relaxation rate in the ordered state follows the $T^3$ behavior indicative of the two-magnon Raman process. The spin lattice of KBaCr${}_2$(PO${}_4$)${}_3$ comprises two crystallographically nonequivalent ferromagnetic sublattices that are coupled antiferromagnetically, thus eliminating frustration in this trillium network.

12 pages, 13 figures