Giant Magnetoresistance in Carbon Nanotubes with Single-Molecule Magnets TbPc₂

Abstract

We present experimental results and a theoretical model for the gate-controlled spin-valve effect in carbon nanotubes with side-attached single-molecule magnets TbPc (Terbium(III) bis-phthalocyanine). These structures show a giant magnetoresistance up to 1000% in experiments on single-wall nanotubes that are tunnel-coupled to the leads. The proposed theoretical model combines the spin-dependent Fano effect with Coulomb blockade and predicts a spin-spin interaction between the TbPc molecules, mediated by conducting electrons via the charging effect. This gate-tuned interaction is responsible for the stable magnetic ordering of the inner spins of the molecules in the absence of magnetic field. In the case of antiferromagnetic arrangement, electrons with either spin experience the scattering by the molecules, which results in blocking the linear transport. In strong magnetic fields, the Zeeman energy exceeds the effective antiferromagnetic coupling and one species of electrons is not scattered by molecules, which leads to a much lower total resistance at the resonant values of gate voltage, and hence to a supramolecular spin-valve effect.

Tuning of a Vertical Spin Valve with a Monolayer of Single Molecule Magnets

“…More probably charge transfer can occur here through the singly occupied molecular orbital delocalized on the phthalocyaninato ligands. Carriers can feel the magnetic moment of the SMM through space (dipolar interaction) or through a weak, bond‐mediated, exchange interaction . We remind that the TbPc 2 system has its own intrinsic dynamics defined by its characteristic relaxation time τ introduced in paragraph 2.1.…”

Dysprosium magnesium silicate apatite featuring field and temperature stable slow magnetization relaxation

“…To date hundreds of coordination compounds of open shell dand f-metals have been shown to exhibit magnetic bistability of a lone metal ion and are referred to as single ion magnets (SIMs) with potential applications in super-dense information recording, molecular electronics, spintronics, and quantum computing. [1][2][3][4][5][6] Their key parametersthe energy barrier for magnetization reversal U eff and magnetization blocking temperature T b (the temperature at which the hysteresis loop closes)lately have been strongly improved and currently approach 1540 cm À1 and 80 K, respectively. [7][8][9][10] Open shell metal ions embedded in a diamagnetic ceramic inorganic matrix constitute a special class of such materials.…”

“…[14][15][16][17] Presence of such interactions is also important in order to correlate spins of magnetic centers, which is a necessary prerequisite for establishing qubits for quantum computers. 4,5 Therefore compounds with relatively short distance between paramagnetic centers (however not magnetically long-range ordered) may be of pertinent interest. latter compounds exhibit fast magnetization relaxation in the absence of an external magnetic eld, but with increasing eld slow relaxation paths gradually arise.…”

Self‐Assembly of TbPc2 Single‐Molecule Magnets on Surface through Multiple Hydrogen Bonding

“…Thanks to the field dependence of the maximum of the XMCD in the Tb edge, normalized with the isotropic spectra, it is possible to follow the magnetization dependence of the self‐assembled complex with the magnetic field (Figure b) revealing clearly that the TbPc 2 behavior is essentially unaltered with respect to the bulk sample measured under similar conditions. The adopted procedure allows to transfer unaltered the SMMs properties to the Si surface, an uncommon result for a monolayer of TbPc 2 , which properties are often affected by the nanostructuration procedure, excluding noncovalent interaction of pyrene‐functionalized units with graphene substrates . The adopted multitechnique characterization protocol suggests that the multiple hydrogen bonding strategy can allow a mild and controlled chemisorption of the molecular layer that could be extended also to other surfaces in the future allowing in all cases an efficient decoupling of the SMM core from the surface.…”

“…This result highlights the needs for the development of alternative chemisorption approaches. So far, most of the activity of TbPc 2 assembling has been focused on the noncovalent anchoring through π–π interactions and via S‐Au monolayer assembling . However, these protocols suffer from the inherent low stability of the resulting layer due to the weakness of the interactions involved.…”