Ising-like anisotropy stabilized 13 and 23 magnetization plateaus in the V3+ kagome lattice antiferromagnets Cs2KV3F12,Cs2NaV3F12 , and Rb2NaV3F12

Abstract

We have investigated crystal structure and magnetic properties of three $S=1\phantom{\rule{4pt}{0ex}}{\mathrm{V}}^{3+}$ Ising-like anisotropic kagome lattice antiferromagnets, ${\mathrm{Cs}}_{2}\mathrm{K}{\mathrm{V}}_{3}{\mathrm{F}}_{12},{\mathrm{Cs}}_{2}\mathrm{Na}{\mathrm{V}}_{3}{\mathrm{F}}_{12}$, and ${\mathrm{Rb}}_{2}\mathrm{Na}{\mathrm{V}}_{3}{\mathrm{F}}_{12}$, using single crystals. Each compound crystallizes in a monoclinic system and has a slightly distorted kagome lattice. Although the magnetic properties are similar, the details depend on the magnitude of magnetic anisotropy. The magnetization and magnetic susceptibility are highly anisotropic owing to anisotropic $g$ factors and Ising-like single ion anisotropy originating from partially unquenched orbital moments of ${\mathrm{V}}^{3+}$, and the easy axis of Ising-like anisotropy is perpendicular to the kagome plane. In contrast to disordered ground states in the isostructural ${\mathrm{Ti}}^{3+}$ $(S=1/2)$ compounds, the ${\mathrm{V}}^{3+}$ $(S=1)$ compounds exhibit antiferromagnetic ordering with distorted ${120}^{\ensuremath{\circ}}$ structure or other nearly coplanar magnetic structure whose basal spin plane includes the easy axis, which is mainly due to large magnetic anisotropy and decrease of quantum fluctuation. Moreover, when magnetic fields are applied perpendicular to the kagome plane, magnetization curves of them show distinct 1/3 and 2/3 magnetization plateaus, which are stabilized by Ising-like single ion anisotropy. In particular, the 2/3 magnetization plateaus are notable magnetic phenomena in kagome lattice antiferromagnets and are due to the combination of spin frustration, Ising-like single ion anisotropy, and the small monoclinic distortion of kagome lattices.