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(2)O)Mo(CN)(8)]·H(2)O (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(∥)/k(B) = -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(⊥)/k(B) = -1.0 K. For the compound [Sm(pzam)(3)(H(2)O)Mo(CN)(8)]·H(2)O 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.

Realization of the one-dimensional anisotropicXYmodel in a Tb(III)-W(V) chain compound

“…As a matter of fact, the compounds containing Sm(III) and Gd(III) ions show a transition to 3D long-range magnetic order at TC  0.6 K and TC  0.7 K, respectively. [8][9] A similar magnetic transition is observed at TC  1 K for the Tb(III) analogue. [7] From the comparison of the (isostructural) complexes [Gd(pzam)3(H2O)M(CN)8]H2O (M = Mo and W), it appeared that the strength of the isotropic exchange interaction increases by replacing Mo(V) with W(V), probably as a result of the larger radial extent of the magnetic 5d orbitals.…”

“…Previously, we reported the synthesis and magnetothermal studies of heterometallic rareearth (RE) -based cyanido-bridged 1D complexes, namely, [RE(pzam) 3 (H 2 O)Mo(CN) 8 ]·H 2 O (RE = Nd, Sm, Gd, Tb, and Er, pzam = pyrazine-2-carboxamide), whose magnetic properties are mainly determined by the particular RE ion involved. [7][8][9][10][11] We found that the Nd(III) and Mo(V) ions are coupled ferromagnetically into magnetic chains by an XY -type (planar) interaction. 10 The interaction between Tb(III) and Mo(V) is likewise ferromagnetic, but with a strong Isingtype anisotropy.…”

“…8 An antiferromagnetic interaction is also observed between Sm(III) and Mo(V) as well as Er(III) and Mo(V), respectively. 9 The symmetry of the interaction is Ising-Heisenberg in the case of Sm(III), whereas the compound with Er(III) behaves as a pure XY chain. 9 Although long-range order in pure 1D materials has to occur at T = 0 K, the presence of interchain interactions, albeit weak, shifts the ordering temperature to a finite value.…”

“…9 The symmetry of the interaction is Ising-Heisenberg in the case of Sm(III), whereas the compound with Er(III) behaves as a pure XY chain. 9 Although long-range order in pure 1D materials has to occur at T = 0 K, the presence of interchain interactions, albeit weak, shifts the ordering temperature to a finite value. As a matter of fact, the compounds containing Sm(III) and Gd(III) ions show a transition to three-dimensional (3D) long-range magnetic order at T C ∼ = 0.6 K and T C ∼ = 0.7 K, respectively.…”

Rationalization of the Lanthanide-Ion-Driven Magnetic Properties in a Series of 4f–5d Cyano-Bridged Chains

“…Previously, we reported a detailed experimental study of the magnetic properties of one-dimensional d–f cyanido-bridged assemblies derived from [M(CN) 8 ] 3– and [RE(pzam) 3 ] 3+ building blocks (M = Mo(V), W(V), RE = rare earth ions, pzam = pyrazine-2-carboxamide). , In several cases, we performed the fit of the exchange interactions between neighboring metal ions and their correlation to the structure. In this paper, we report experimental and theoretical studies on the isostructural family [RE(pzam) 3 (H 2 O)W(CN) 8 ]·H 2 O (RE(III) = Gd, Tb, Dy).…”