Spin Photovoltaic Effect on Molecule Coupled Ferromagnetic Films of a Magnetic Tunnel Junction

Abstract

Economical solar energy harvesting can be boosted by the discovery of fundamentally new photovoltaic mechanism, and a suitable system to realize it with commonly available materials. One promising route is to focus on spin property of the electron, not charge, and develop spin photovoltaic effect with widely available ferromagnetic metals like iron and nickel. This paper reports the observation of photovoltaic effect on the molecular spintronics device composed of a magnetic tunnel junctions (MTJ) testbed and organometallic molecular clusters (OMCs). Our MSDs were produced by bridging the OMC channels between the ferromagnetic films of a prefabricated MTJ testbed with exposed side edges. The MTJ testbed exhibited OMC induced strong increase in exchange coupling and photovoltaic effect. Control experiments on isolated ferromagnetic films, same as utilized in the MTJ testbed, suggested that OMCs neither affected the magnetic properties nor produced any photovoltaic effect. Photovoltaic effect was only observed on the pair of ferromagnetic films serving as magnetic electrodes in a MTJ. Our recent Monte Carlo simulations and multiple magnetic characterizations provide evidence that molecules induced strong coupling between two ferromagnetic films can dramatically alter the overall magnetic properties of a MTJ; presumably making an ordinary MTJ suitable for spin based photovoltaic effect. The photovoltaic effect on our molecular spintronics devices (MTJ+OMCs) was sensitive towards the external magnetic field and temperature. Present paper motivates further studies to understand the spin photovoltaic effect in molecular spintronics devices.