Room-temperature generation of giant pure spin currents using epitaxial Co2FeSi spin injectors

Abstract

The generation, manipulation and detection of a pure spin current (i.e., the flow of spin angular momentum without a charge current) are prospective approaches for realizing next-generation spintronic devices with ultra-low electric power consumption. Conventional ferromagnetic electrodes such as Co and NiFe have been utilized as spin injectors to generate pure spin currents in nonmagnetic channels. However, the generation efficiency of pure spin currents is extremely low at room temperature, giving rise to a serious obstacle for device applications. Here we demonstrate the generation of giant pure spin currents at room temperature in lateral spin valve devices with a highly ordered Heusler-compound Co2FeSi (CFS) spin injector. The generation efficiency of pure spin currents from the CFS spin injectors is 10 times greater than that of the NiFe injectors, indicating that Heusler compound spin injectors with high spin polarization enable us to materialize a high-performance lateral spin device. The present study is a technological jump in spintronics, and indicates the great potential of ferromagnetic Heusler compounds with half metallicity for generating pure spin currents. Takashi Kimura, Kohei Hamaya and co-workers have generated large pure spin currents at room temperature, with high efficiency. Spintronic devices, which use the spin of electrons as well as their charge, promise to be faster and less power-consuming than traditional charge-based electronic ones. A pure spin current — a flow that is not accompanied by charge current — seems to be a promising way to write information for such devices. However, although ‘spin injectors’ capable of creating such currents have been developed, their efficiency has generally remained too low for practical applications. Now, Kimura, Hamaya and colleagues have significantly improved this efficiency by using a highly ordered cobalt-iron-silicon ‘Heusler’ compound with high spin polarization. These findings highlight the potential of Heusler compounds as spin injectors, and move the construction of functional spintronic devices one step forward. Heusler compound spin injector with a high spin polarization dramatically improves the generation efficiency of the pure spin current compared with a conventional ferromagnetic metal.