Room-temperature spin-dependent tunneling through molecules

Abstract

We have fabricated assemblies of molecular junctions comprised of superparamagnetic Fe3O4 nanoparticles self-assembled with alkane molecules of different lengths as the spacer. The electrical resistance increases exponentially over nearly two decades as the molecular length varies from 0.7 to 2.5 nm, indicating that electrons tunnel through the molecules that are chemically bonded with Fe3O4 nanoparticles. Up to ∼21% room-temperature magnetoresistance is observed. Remarkably, the tunneling magnetoresistance ratio stays nearly independent of molecular length, which entails room-temperature spin-conserving transport in organic molecules.

Magnetization enhancement in magnetite nanoparticles capped with alginic acid

“…This obstacle can be overcame by capping the magnetic nanoparticles with various polymers [23][24][25][26] and organic acid, which in some cases allows restoration of the surface magnetism [27][28][29]. The best capping materials for medical applications are obviously organic ones like oleic and aliphatic acids [30], oleic acid with oleyamine [27], stearic acid [31], sulphamic acid [32], and many others [33]. One of the new capping materials is alginic acid -a cheap, common and nontoxic natural biopolymer [34][35][36] used already in food industry as a gelling agent or flavorless gum (sodium alginate E401).…”

Printable Giant Magnetoresistive Devices

“…Typically, these granular metallic composites reveal only a relatively small GMR effect at room temperature 15. Very recently, room temperature tunnelling magnetoresistance has been achieved in hybrid systems containing magnetic particles covered by an organic shell 17–21. However these composites exhibits small conductivity (∼10 −7 S/m) with resistances for micrometre sized structures in the range of 10 9 Ohm, which is unacceptably high for printable electronics 20, 21.…”

“…Very recently, room temperature tunnelling magnetoresistance has been achieved in hybrid systems containing magnetic particles covered by an organic shell 17–21. However these composites exhibits small conductivity (∼10 −7 S/m) with resistances for micrometre sized structures in the range of 10 9 Ohm, which is unacceptably high for printable electronics 20, 21. In addition to the spintronics based on magnetic multilayers, recent theoretical works are dealing with alternatives based on graphene 22, 23.…”

Enhancing magnetoresistance in tetrathiafulvalene carboxylate modified iron oxide nanoparticle assemblies

“…1,2 This non-conductive coating can be a layer of inorganic oxide or organic surfactant. [3][4][5][6][7][8][9][10][11] Due to its insulating nature, the surfactant does not have the strong spin-orbit coupling and hyperfine interaction with the NP, and as a result, it serves as an electron spin divider between two adjacent NPs, increasing the spin relaxation time of each NP and enhancing the MR effect on the spin-dominated electron transport. In this array, electrons are transported across two adjacent NPs with their conductivity controlled by the length of the surfactant and the cross-surfactant interactions.…”

“…In this array, electrons are transported across two adjacent NPs with their conductivity controlled by the length of the surfactant and the cross-surfactant interactions. [3][4][5][6][7][8][9][10][11] Due to its insulating nature, the surfactant does not have the strong spin-orbit coupling and hyperfine interaction with the NP, and as a result, it serves as an electron spin divider between two adjacent NPs, increasing the spin relaxation time of each NP and enhancing the MR effect on the spin-dominated electron transport. [12][13][14] Recent advances in NP syntheses further allow the preparation of magnetic NPs with NP dimensions controlled at the near-atomic-scale precision, [15][16][17] and consequently, the bonding interactions between the organic layer and the ferromagnetic surface can be controlled and the spin-dependent transport may be tuned to optimization.…”