Giant magnetoresistance in organic spin-valves

Abstract

A spin valve is a layered structure of magnetic and non-magnetic (spacer) materials whose electrical resistance depends on the spin state of electrons passing through the device and so can be controlled by an external magnetic field. The discoveries of giant magnetoresistance and tunnelling magnetoresistance in metallic spin valves have revolutionized applications such as magnetic recording and memory, and launched the new field of spin electronics--'spintronics'. Intense research efforts are now devoted to extending these spin-dependent effects to semiconductor materials. But while there have been noteworthy advances in spin injection and detection using inorganic semiconductors, spin-valve devices with semiconducting spacers have not yet been demonstrated. pi-conjugated organic semiconductors may offer a promising alternative approach to semiconductor spintronics, by virtue of their relatively strong electron-phonon coupling and large spin coherence. Here we report the injection, transport and detection of spin-polarized carriers using an organic semiconductor as the spacer layer in a spin-valve structure, yielding low-temperature giant magnetoresistance effects as large as 40 per cent.

Observation of a large spin-dependent transport length in organic spin valves at room temperature

“…Nevertheless, the thickness of the OS layer is generally limited to around several nanometres, as the magnetoresistance (MR) ratio decays sharply, and subsequently disappears with increasing OS thickness. The observation of SDT in OSs in the hopping process has also been reported 2,3 in such materials as tris (8-hydroxyquinolinato) aluminium (Alq 3 ) and rubrene. However, most studies have only been carried out at low temperatures because of the evident reduction in the SDT length with increasing measurement temperatures until the MR effect finally disappears at room temperature 2,[13][14][15][16][17][18][19] .…”

“…OSs are expected to possess a large spin-dependent transport (SDT) length due to their weak spin-orbit coupling and weak hyperfine interaction [1][2][3][4][5][6] . The SDT phenomenon at room temperature via a tunnelling mechanism has been studied in several different OSs [7][8][9][10][11][12] .…”

“…Most importantly, a large SDT length of approximately 110 nm was experimentally observed in the C 60 layer at room temperature. This research may strongly motivate the development of spin-based organic devices, such as organic spin valves [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] and spin-based organic light-emitting diodes 20 .…”

Hyperfine Interactions in Graphene and Related Carbon Nanostructures

“…Carbon nanostructures are attractive for these applications because of the weak spin-orbit interaction in materials made of light elements [4,5]. Promising results for the spin-polarized current lifetimes in carbon nanotubes [6,7,8] and graphene [9] unambiguously confirm the potential of these materials.…”

“…Jp, 81.05.Uw, 03.67.Pp Graphene and related carbon nanostructures are considered as potential building blocks of future electronics, including spintronics [1] and quantum information processing based on electron spins [2] or nuclear spins [3]. Carbon nanostructures are attractive for these applications because of the weak spin-orbit interaction in materials made of light elements [4,5]. Promising results for the spin-polarized current lifetimes in carbon nanotubes [6,7,8] and graphene [9] unambiguously confirm the potential of these materials.…”