Precise evaluation of small spin-dependent Seebeck coefficient for Permalloy using lateral spin valve

Efficient generation and detection of the spin current is a crucial issue for the application of spintronic devices. In addition, integrating spintronic circuit with conventional semiconductor devices is another important milestone for the practical application of the spin devices. Recently, the interplay between the heat and spin has attracted great attention because the temperature gradient is found to generate the spin current [1]. Since the heat can generate and propagate without electricity, this novel approach using the heat may open a new avenue for simplifying integration of spin devices. The precise estimation of the spin-dependent Seebeck coefficient (S_s), which is one of the important factors for the efficient generation of the thermal spin current, is indispensable to develop and optimize the spin device structure using the heat. However, it is still a hard nut to crack for the conventional ferromagnet because of its small magnitude and tiny related spin signal. Moreover, the related spin signal is smeared out by the spurious signals induced by classical thermoelectric effects especially at room temperature. Recently, we have shown that both the electrically and thermally driven spin injection efficiencies have been dramatically enhanced by the CoFeAl electrodes because of the excellent property for the thermal spin injection and electrical spin detection of CoFeAl [2]. In this presentation, by using the excellent CoFeAl, we develop the precise evaluation method for the thermal spin injection properties of Permalloy (Py)/Cu hybrid in lateral spin valve structure.