Spin and charge thermopower effects in the ferromagnetic graphene junction

Abstract

Using wave function matching approach and employing the Landauer-Buttiker formula a ferromagnetic graphene junction with temperature gradient across the system, is studied. We calculate the thermally induced charge and spin current as well as the thermoelectric voltage (Seebeck effect) in the linear and nonlinear regimes. Our calculation revealed that owing to the electron-hole symmetry, the charge Seebeck coefficient is, for an undoped magnetic graphene, an odd function of chemical potential while the spin Seebeck coefficient is an even function regardless of the temperature gradient and junction length. We have also found with an accurate tuning external parameter, namely the exchange filed and gate voltage, the temperature gradient across the junction drives a pure spin current without accompanying the charge current. Another important characteristic of thermoelectric transport, thermally induced current in the nonlinear regime, is examined. It would be our main finding that with increasing thermal gradient applied to the junction the spin and charge thermovoltages decrease and even become zero for non zero temperature bias.

Enhancing thermoelectric properties through a three-terminal benzene molecule

“…As these factors are correlated, increasing ZT to values greater than unity is challenging. One promising approach has been to reduce the contribution of phonons by nanostructuring materials 5 .…”

Spin-caloritronic transport in hexagonal graphene nanoflakes

“…The effects of a substrate on the TEP have also been explored by depositing graphene on boron nitride to suppress the disorder, which has led to a large enhancement of the TEP [26]. The charge and spin Seebeck effects in ferromagnetic graphene have been studied by one of the present authors, showing that a pure spin current with a large spin figure of merit is attainable by varying the spin splitting, temperature, and doping of the junction [27]. Further studies concern rectangular rings [28] and bilayer graphene flakes [29].…”

“…Graphene's distinguished thermal and electronic performance render it one of the most outstanding candidates in spin caloritronics. Many experimental and theoretical works have investigated the thermally-induced spin-transport properties of graphene [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]. Some of these works [23][24][25][26][27][28][29] focused on the electronic properties of graphene.…”

“…Many experimental and theoretical works have investigated the thermally-induced spin-transport properties of graphene [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]. Some of these works [23][24][25][26][27][28][29] focused on the electronic properties of graphene. In particular, the sign inversion behavior of graphene's thermoelectric power (TEP) across the charge neutrality point and the gate dependence of the TEP have been measured by Zuev et al [23].…”

Metal-free magnetism, spin-dependent Seebeck effect, and spin-Seebeck diode effect in armchair graphene nanoribbons

“…To use SSE in practical device applications 9 – 11 , the spin-Seebeck diode (SSD) effect 12 – 14 , which allows the thermal-induced spin currents to flow in only one direction and be rectified, is required. In recent years, there have been many reports concerning these effects 15 – 18 . Zeng et al .…”