Manipulation of Giant Field-Like Spin Torque in Amine-Ended Single-Molecule Magnetic Junctions

Abstract

We propose a comprehensive theoretical investigation for the angular, external bias and mechanical strain dependence of the giant field-like spin torque (FLST) effect for amine-ended Co/BDA/Co single-molecule magnetic junctions in the non-collinear magnetic configuration, by employing our newly developed nonequilibrium Green’s function method within the framework of density functional theory. In sharp contrast to the conventional Co/vacuum/Co magnetic tunnel junction, the hard–hard coupling between the amine linker and the Co tip atom plays an active role in the interfacial spin filter to emerge the strong interlayer exchange coupling between two Co electrodes and the anomalous strain-enhanced FLST effect. These intriguing features may pave a novel way to engineer the magnetization switching via either external bias or mechanical strain to achieve the writing process in next-generation multifunctional organic FLST-MRAMs with lower power consumption.

Determination of Perpendicular Magnetic Anisotropy in Fe/MgO/Fe Magnetic Tunnel Junction: A DFT-Based Spin-Orbit Torque Approach

“…Finally, the physical quantities including the spin current accumulation and spin torque are calculated by our developed JunPy package using the self-consistent Hamiltonian above [34]. Also, the divide-and-conquer (DC) technique is used to study the atom-resolved quantities in the semi-infinite electrodes [7].…”

Observation on Volatile and Nonvolatile Magnetic Reversions Mediated by Electric Current in Highly Conductive Gd3Fe5O12

“…Modulating magnetization with electric currents has attracted intense interests since the correlations between charge and spin are fundamentally essential and current-based devices are compatible with modern electronics. Traditionally, magnetization switching is accomplished by exerting a magnetic field generated by electric currents, which is known to suffer from large energy consumptions since high current density (>10 5 A/cm 2 ) is needed. − It is also possible to flip the magnetic moments via injecting spin torques carried by spin currents, including the spin-transfer-torque (STT) mechanism and the spin-orbit-torque (SOT) mechanism. − These two methods have been achieved in several systems, e.g., CoFeGe, Fe/GdAs/GaMnAs, and Bi 2 Se 3 /NiFe. − To date, the desired spin currents can be converted from charge currents, utilizing the spin filtering effect in half metal layers or the spin Hall effects in heavy metal layers. Yet, the magnitude of spin torque carried on currents is small compared to the intrinsic torques in conventional magnetic materials.…”

Effect of Contact Geometry on Spin Transport in Amine-Ended Single-Molecule Magnetic Junctions

“…The amine linker plays an important role to provide efficient spin-selective transport properties, 29,30 anomalous magnetoresistance, 31 and the giant nonlocal field-like spin torque effect. 32 Unlike the dative interaction between amine and Au in nonmagnetic SMJs, the strong coupling between the hard metal (Co) and hard base (N) in SMMJs instead favors the covalent bonding between the H-dissociated amine linker and Co adatom and may even provide variability in the linker− electrode contact geometry, which are crucial but remain unclear during the fabrication of real SMMJs, especially for breaking junction techniques.…”

“…Recent theoretical works proposed a new type of single-molecule magnetic junctions (SMMJs) with strong hard–hard coupling between the amine linker and ferromagnetic electrode, which provide an additional degree of freedom of spin to control the electronic signal since the spin momentum of electrons can be well preserved in a diffusion length of hundreds of nanometers due to weak spin–orbit coupling. The amine linker plays an important role to provide efficient spin-selective transport properties, , anomalous magnetoresistance, and the giant nonlocal field-like spin torque effect . Unlike the dative interaction between amine and Au in nonmagnetic SMJs, the strong coupling between the hard metal (Co) and hard base (N) in SMMJs instead favors the covalent bonding between the H-dissociated amine linker and Co adatom and may even provide variability in the linker–electrode contact geometry, which are crucial but remain unclear during the fabrication of real SMMJs, especially for breaking junction techniques.…”