Enhancement of thermal spin signal and suppression of anomalous Nernst effect in the CoFeAl/Cu/CoFeAl lateral spin valve

Generation of large spin current is an important issue in the operation of spintronic devices because the spin current plays a key role in spin-dependent transports and spin-transfer switching. Recently, a heat flow across a ferromagnet (FM) / nonmagnet (NM) junction is found to be able to generate and propagate the spin current. We have found that the large spin current is efficiently produced by using a heat flow across the CoFeAl /Cu junction because of the relatively large spin-dependent Seebeck coefficient for CoFeAl. The generated spin current is, in general, detected as the electrical voltage by using another ferromagnetic electrode. Using the nonlocal electrical detection scheme, one can prevent the background signal due to the spin-independent charge current. However, in the case of the thermal spin injection, the heat current reaches at the nonlocal ferromagnetic electrode and produces classical thermoelectric effects such as anomalous Nernst effect. Such spurious signals becomes serious obstacle when the large spin current is generated by the thermal spin injection. Therefore, the optimization of the device structure is indispensable for the ideal generation of the spin current using the heat. Here, we explore better geometry for generating the thermally excited spin signal in a laterally configured FM/NM hybrid nanostructure.