title: Longitudinal spin Seebeck effect: from fundamentals to applications.
abstract: The spin Seebeck effect refers to the generation of spin voltage as a result of a temperature gradient in ferromagnetic or ferrimagnetic materials. When a conductor is attached to a magnet under a temperature gradient, the thermally generated spin voltage in the magnet injects a spin current into the conductor, which in turn produces electric voltage owing to the spin-orbit interaction. The spin Seebeck effect is of increasing importance in spintronics, since it enables direct generation of a spin current from heat and appears in a variety of magnets ranging from metals and semiconductors to insulators. Recent studies on the spin Seebeck effect have been conducted mainly in paramagnetic metal/ferrimagnetic insulator junction systems in the longitudinal configuration in which a spin current flowing parallel to the temperature gradient is measured. This 'longitudinal spin Seebeck effect' (LSSE) has been observed in various sample systems and exclusively established by separating the spin-current contribution from extrinsic artefacts, such as conventional thermoelectric and magnetic proximity effects. The LSSE in insulators also provides a novel and versatile pathway to thermoelectric generation in combination of the inverse spin-Hall effects. In this paper, we review basic experiments on the LSSE and discuss its potential thermoelectric applications with several demonstrations.
authors.affiliation: Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan. PRESTO, Japan Science and Technology Agency, Saitama 332-0012, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Uchida
authors.forename: M
authors.initials: M
authors.lastname: Ishida
authors.forename: T
authors.initials: T
authors.lastname: Kikkawa
authors.forename: A
authors.initials: A
authors.lastname: Kirihara
authors.forename: T
authors.initials: T
authors.lastname: Murakami
authors.forename: E
authors.initials: E
authors.lastname: Saitoh