Introducing immobilized metal phthalocyanines as spin-injection and detection layers in organic spin-valves: Spin-tunneling and spin-transport regimes

In (organic) spin-valve devices, two ferromagnetic electrodes having different coercive fields are used to achieve an anti-parallel configuration necessary to enforce spin-flip of electrons within the semiconductor spacer layer. Here we report a use of immobilized magnetic organic molecules as spin-injection and spin-detection layers to form pre-fabricated spin-valve devices. While immobilized manganese- and nickel-phthalocyanines were used as spin-injection and spin-detection layers both, copper phthalocyanine acted as the spacer layer in the all-organic spin-valve devices.In the current-voltage characteristics of parallel and anti-parallel configurations, the electrical resistance was always higher for the latter one implying positive magnetoresistance in the material. By lowering thickness of the spacer layer down to a monolayer region, a tunneling regime could be achieved; spin-flip process in organic spin-valves has been found to be facile in the tunneling regime as compared to that during the spin-transport process through a thicker spacer layer.