Control Of Magnetic Interactions Research Articles

Carbon‐based organic radical spin filters

AbstractSingle‐molecule magnetic junctions serve as an important component for the manipulation of spin‐polarized currents by chemical modifications and control of magnetic interactions in spintronic devices. We employed the nonequilibrium green function and spin‐polarized density functional theory simulations to investigate the performance of molecular junctions bearing an organic radical as spin filters. A spin‐polarized current could be generated using the junctions and, moreover, the spin‐filtering efficiency could be tuned by varying the number of magnetic units. Spin orbital and density of states analyses revealed the relationship effect of the shapes and energy levels of the dominant electron‐conducting channels in the spin‐filtering efficiency. Thus, the use of a tunable organic magnetic molecular junction system is an appealing approach for regulating spin‐polarized currents in spintronic devices.

Stabilization of a honeycomb lattice of IrO6 octahedra by formation of ilmenite-type superlattices in MnTiO3

In quantum spin liquid research, thin films are an attractive arena that enables the control of magnetic interactions via epitaxial strain and two-dimensionality, which are absent in bulk crystals. Here, as a promising candidate for the development of quantum spin liquids in thin films, we propose a robust ilmenite-type oxide with a honeycomb lattice of edge-sharing IrO6 octahedra artificially stabilised by superlattice formation using the ilmenite-type antiferromagnetic oxide MnTiO3. Stabilised sub-unit-cell-thick Mn–Ir–O layers are isostructural to MnTiO3 and have an atomic arrangement corresponding to ilmenite-type MnIrO3. By performing spin Hall magnetoresistance measurements, we observe that antiferromagnetic ordering in the ilmenite Mn sublattice is suppressed by modified magnetic interactions in the MnO6 planes via the IrO6 planes. These findings contribute to the development of two-dimensional Kitaev candidate materials, accelerating the discovery of exotic physics and applications specific to quantum spin liquids.

Control of magnetic interactions between surface adatoms via orbital repopulation

We propose a reversible mechanism for switching Heisenberg-type exchange interactions between deposited transition metal adatoms from ferromagnetic to antiferromagnetic. Using first-principles calculations, we show that this mechanism can be realized for cobalt atoms on the surface of black phosphorus by making use of electrically-controlled orbital repopulation, as recently demonstrated by scanning probe techniques [Nat. Commun. 9, 3904 (2018)]. We find that field-induced repopulation not only affects the spin state, but also causes considerable modification of exchange interaction between adatoms, including its sign. Our model analysis demonstrates that variable adatom-substrate hybridization is a key factor responsible for this modification. We perform quantum simulations of inelastic tunneling characteristics and discuss possible ways to verify the proposed mechanism experimentally.

Phase-shift control of the exchange coupling between magnetic impurities

The control of magnetic interactions is one of the most relevant topics in spintronics. In this work, we propose to use electric potential barriers for tuning or even suppressing the RKKY exchange coupling between magnetic impurities in a two-dimensional electron gas. Our results show that it is possible to manipulate both the magnitude and sign of the RKKY coupling. Systems with two and three impurities are studied. In the last case, the use of two potential barriers can be employed to decouple one of the impurities to the rest. The possibility to control the interactions between magnetic atoms individually may have applications in neuromorphic and quantum computing.

Aggregation state and magnetic properties of magnetite nanoparticles controlled by an optimized silica coating

The control of magnetic interactions is becoming essential to expand/improve the applicability of magnetic nanoparticles (NPs). Here, we show that an optimized microemulsion method can be used to obtain homogenous silica coatings on even single magnetic nuclei of highly crystalline Fe3−xO4 NPs (7 and 16 nm) derived from a high-temperature method. We show that the thickness of this coating is controlled almost at will allowing much higher average separation among particles as compared to the oleic acid coating present on pristine NPs. Magnetic susceptibility studies show that the thickness of the silica coating allows the control of magnetic interactions. Specifically, as this effect is better displayed for the smallest particles, we show that dipole-dipole interparticle interactions can be tuned progressively for the 7 nm NPs, from almost non-interacting to strongly interacting particles at room temperature. The quantitative analysis of the magnetic properties unambiguously suggests that dipolar interactions significantly broaden the effective distribution of energy barriers by spreading the distribution of activation magnetic volumes.

ChemInform Abstract: Control of Magnetic Interactions in Polyarylmethyl Triplet Diradicals Using Steric Hindrance

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Control of magnetic interactions in polyarylmethyl triplet diradicals using steric hindrance

Control of magnetic interactions in polyarylmethyl triplet diradicals using steric hindrance