Quasi-two-dimensional antiferromagnet on a triangular lattice RbFe ( MoO 4 ) 2

摘要: $\mathrm{RbFe}({\mathrm{MoO}}_{4}{)}_{2}$ is a rare example of nearly two-dimensional Heisenberg antiferromagnet on triangular lattice. Magnetic resonance spectra and magnetization curves reveal that the system has layered spin structure with six magnetic sublattices. The sublattices within layer are arranged in manner vectors $120\ifmmode^\circ\else\textdegree\fi{}$ apart. $H\ensuremath{-}T$ phase diagram, containing at least five different phases constructed. In zero field, undergoes transition ${T}_{N}=3.8\mathrm{K}$ into noncollinear all spins confined basal plane. application an in-plane field induces collinear state between fields ${H}_{c1}=47\mathrm{kOe}$ ${H}_{c2}=71\mathrm{kOe}$ produces plateau one-third saturation moment. Both ESR measurements also clearly indicate additional first-order 35 kOe. exact nature this uncertain.