4 research outputs found
Proposal for a Dual Spin Filter Based on [VO(C<sub>3</sub>S<sub>4</sub>O)<sub>2</sub>]<sup>2ā</sup>
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 [VOĀ(C<sub>3</sub>S<sub>4</sub>O)<sub>2</sub>]<sup>2ā</sup> 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><sub>g</sub> = ā0.51 V, but
a small shift to <i>V</i><sub>g</sub> = ā0.63 V is
capable of switching to spin-down transport. For both cases, we estimate
a large low-bias conductance (approximately 2 Ī¼S at <i>V</i><sub>bias</sub> < 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 fāBlock 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 metalāligand
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 [LnĀ(W<sub>5</sub>O<sub>18</sub>)<sub>2</sub>]<sup>9ā</sup> and [LnĀ(Ī²<sub>2</sub>-SiW<sub>11</sub>O<sub>39</sub>)<sub>2</sub>]<sup>13ā</sup> (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, [NdĀ(W<sub>5</sub>O<sub>18</sub>)<sub>2</sub>]<sup>9ā</sup> 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<sup>ā1</sup> under an applied dc field of 1000 Oe, this is the second example
of a Nd<sup>3+</sup>-based single-ion magnet
Magnetic Properties of the Layered Lanthanide Hydroxide Series Y<sub><i>x</i></sub>Dy<sub>8āx</sub>(OH)<sub>20</sub>Cl<sub>4</sub>Ā·6H<sub>2</sub>O: 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 = Dy<sub>8</sub>(OH)<sub>20</sub>Cl<sub>4</sub>Ā·6H<sub>2</sub>O). 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 DyāDy 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 DyāOāDy
angles