Short-range correlations in d-f cyanido-bridged assemblies with XY and XY-Heisenberg anisotropy

Abstract

Two new d-f cyanido-bridged 1D assemblies [RE(pzam)3(H 2O)Mo(CN)8]·H2O (RE = Sm(iii), Er(iii)) were synthesized and their magneto-structural properties have been studied by field-dependent magnetization and specific heat measurements at low temperatures (≥0.3 K). Below ≈ 10 K the ground state of both the Sm(iii) and Er(iii) ions is found to be a Kramers doublet with effective spin S = 1/2. From analyses of the low-temperature magnetic specific heat and magnetization the exchange coupling between these RE(iii) effective spins and the Mo(v) spins S = 1/2 along the structural chains has been determined. It is found to be antiferromagnetic, with J∥/kB = -2.6 K and Ising-Heisenberg symmetry of the interaction (J∥/J = 0.3) for RE = Sm(iii), whereas the compound with RE = Er(iii) behaves as a pure XY chain, with J/kB = -1.0 K. For the compound [Sm(pzam)3(H2O)Mo(CN) 8]·H2O a small λ-type anomaly in the specific heat is observed at about 0.6 K, which is ascribed to a transition to long-range magnetic ordering induced by weak interchain interactions of dipolar origin. No evidence for 3D interchain magnetic ordering is found in the Er(iii) analogue. © The Royal Society of Chemistry 2011.