Proposal for a Dual Spin Filter Based on [VO(C₃S₄O)₂]^2–

Polynuclear magnetic molecules often present dense electronic transmission spectra with many overlapping conduction spin channels. Single-metal complexes display a sparser density of states, which in the presence of a fixed external magnetic field makes them interesting candidates for spin filtering. Here we perform a DFT study of a family of bis- and tris-dithiolate vanadium complexes sandwiched between Au(111) electrodes and demonstrate that [VO­(C₃S₄O)₂]^2– can behave as a dual spin filter. This means that an external electrical stimulus can switch between the selective transmission of spin-up and spin-down carriers. By using an electrostatic gate, we show that the onset for the spin-up conductance is at a voltage <i>V</i>_g = −0.51 V, but a small shift to <i>V</i>_g = −0.63 V is capable of switching to spin-down transport. For both cases, we estimate a large low-bias conductance (approximately 2 μS at <i>V</i>_bias < 50 mV) with excellent spin selectivity (>99.5%). We conclude by commenting on the general molecular requirements for the chemical design of further examples of such spintronics components

Molecular Anisotropy Analysis of Single-Ion Magnets Using an Effective Electrostatic Model

Simple electrostatic models have been shown to successfully rationalize the magnetic properties of mononuclear single molecule magnets based on f-elements and even to predict the direction of the magnetic anisotropy axis in these nanomagnets. In this Article, we go a step forward by showing that these models, conveniently modified to account for the covalency effects, are able to predict not only the easy axis direction but also the three components of the magnetic anisotropy. Thus, by using a lone pair effective charge (LPEC) model we can fully reproduce the angular dependence of the magnetic susceptibility in single crystals of pentamethylcyclopentadienyl-Er-cyclooctatetraene single-ion magnet. Furthermore, the parametrization of the ligands obtained in this study has been extrapolated to successfully reproduce spectroscopic data of a set of mononuclear lanthanoid complexes based on the same kind of ligands, thus emphasizing the predictive character of this model

Construction of a General Library for the Rational Design of Nanomagnets and Spin Qubits Based on Mononuclear f‑Block Complexes. The Polyoxometalate Case

This paper belongs to a series of contributions aiming at establishing a general library that helps in the description of the crystal field (CF) effect of any ligand on the splitting of the J ground states of mononuclear f-element complexes. Here, the effective parameters associated with the oxo ligands (effective charges and metal–ligand distances) are extracted from the study of the magnetic properties of the first two families of single-ion magnets based on lanthanoid polyoxometalates (POMs), formulated as [Ln­(W₅O₁₈)₂]^9– and [Ln­(β₂-SiW₁₁O₃₉)₂]^13– (Ln = Tb, Dy, Ho, Er, Tm, Yb). This effective CF approach provides a good description of the lowest-lying magnetic levels and the associated wave functions of the studied systems, which is fully consistent with the observed magnetic behavior. In order to demonstrate the predictive character of this model, we have extended our model in a first step to calculate the properties of the POM complexes of the early 4f-block metals. In doing so, [Nd­(W₅O₁₈)₂]^9– has been identified as a suitable candidate to exhibit SMM behavior. Magnetic experiments have confirmed such a prediction, demonstrating the usefulness of this strategy for the directed synthesis of new nanomagnets. Thus, with an effective barrier of 51.4 cm^–1 under an applied dc field of 1000 Oe, this is the second example of a Nd³⁺-based single-ion magnet

Magnetic Properties of the Layered Lanthanide Hydroxide Series Y_<i>x</i>Dy_8‑x(OH)₂₀Cl₄·6H₂O: From Single Ion Magnets to 2D and 3D Interaction Effects

The magnetic properties of layered dysprosium hydroxides, both diluted in the diamagnetic yttrium analogous matrix (LYH:0.04Dy), and intercalated with 2,6-naphthalene dicarboxylate anions (LDyH-2,6-NDC), were studied and compared with the recently reported undiluted compound (LDyH = Dy₈(OH)₂₀Cl₄·6H₂O). The Y diluted compound reveals a single-molecule magnet (SMM) behavior of single Dy ions, with two distinct slow relaxation processes of the magnetization at low temperatures associated with the two main types of Dy sites, 8- and 9-fold coordinated. Only one relaxation process is observed in both undiluted LDyH and intercalated compounds as a consequence of dominant ferromagnetic Dy–Dy interactions, both intra- and interlayer. Semiempirical calculations using a radial effect charge (REC) model for the crystal field splitting of the Dy levels are used to explain data in terms of contributions from the different Dy sites. The dominant ferromagnetic interactions are explained in terms of orientations of easy magnetization axes obtained by REC calculations together with the sign of the superexchange expected from the Dy–O–Dy angles