Integer Versus Half-Integer Spin On An Approximate Honeycomb Lattice

Recent interest in honeycomb lattice materials has focused on their potential to host quantum spin liquid (QSL) states. Variations in bond angles and spin allow a range of interesting behaviors on this lattice, from the predicted QSL ground state of the Kitaev model to exotic magnetic orders. Here we report the physical properties of two compounds with rare earths on an approximate honeycomb lattice. The isostructural compounds Nd2S5Sn (J = 9/2) and Pr2S5Sn (J = 4) permit a direct comparison of half-integer versus integer spins on this lattice. We find strikingly different magnetic properties for the two compounds. Nd2S5Sn orders antiferromagnetically at T-N approximate to 2.5 K and undergoes several magnetic transitions to other ordered states under applied field. Pr2S5Sn displays no magnetic ordering transition above T = 0.41 K, and may be proximate to a spin liquid state.