Giant magnetoresistance through a single molecule

Abstract

Magnetoresistance is a change in the resistance of a material system caused by an applied magnetic field. Giant magnetoresistance occurs in structures containing ferromagnetic contacts separated by a metallic non-magnetic spacer, and is now the basis of read heads for hard drives and for new forms of random access memory. Using an insulator (for example, a molecular thin film) rather than a metal as the spacer gives rise to tunnelling magnetoresistance, which typically produces a larger change in resistance for a given magnetic field strength, but also yields higher resistances, which are a disadvantage for real device operation. Here, we demonstrate giant magnetoresistance across a single, non-magnetic hydrogen phthalocyanine molecule contacted by the ferromagnetic tip of a scanning tunnelling microscope. We measure the magnetoresistance to be 60% and the conductance to be 0.26G(0), where G(0) is the quantum of conductance. Theoretical analysis identifies spin-dependent hybridization of molecular and electrode orbitals as the cause of the large magnetoresistance.

Probing crossover from analogous weak antilocalization to localization by an Aharonov-Bohm interferometer on topological insulator surface

“…To experimentally verify our predictions exhibited here, the spin polarized STM technique is required, which we believe is achievable [25,26] …”

Conductance fingerprints of noncollinear magnetic states in single-atom contacts: A first-principles Wannier-functions study

“…[3][4][5][6][7][8] In such experiments, it has been possible to measure the conductance as a function of tip-sample distance from the tunneling to the contact regime. Due to the promise of spintronic devices for future applications with low power consumption and high speed, a recent focus of such contact measurements has been magnetic systems, e.g., spin-valve behavior has been observed in single magnetic molecules or atoms on surfaces 8,9 and the occurrence of the Kondo effect has been found in ferromagnetic atomic contacts. 10 It has been emphasized that the low coordination of the contact atoms in nanoscale junctions leads to an enhanced tendency towards magnetism, e.g., magnetic moments are formed in systems of otherwise nonmagnetic materials.…”

Of interfaces and spin transport across nanoscale layers

“…The use of molecules in spintronics also opens up a connection to single molecule electronics, where individual molecules are considered for electronic devices. Indeed, MR effects have been demonstrated at the single molecule level [10].…”

“…First-principles transport calculations, which might provide such a link, have so far focused on single molecule electronics [143,144,145], where MR effects have been demonstrated with STM [139,10,146]. Single molecules bonded to two electrodes are not, however, a good model for spintronics devices comprising molecular multilayers.…”

“…Calculations have been applied to model currents through through a single molecule attached to two FM metal electrodes [143,144,145,176,177], as they can be realized in STM experiments, for instance, where MR effects have been demonstrated at the single molecule level [10,157,146,158]. A single molecule is however not …”