The Enhancement of Temperature Gradient by Tunneling Spin Scattering in Magnetic Tunnel Junction

Magnetic Random Access Memory (MRAM) has attracted great attention for future nonvolatile memory devices application. However, it is still a challenge to realize the ultra-small, ultra-high-speed, and ultra-low-power consumption in the future MRAM technology [1]. The microwave-assisted switching (MAS) and thermal-assisted switching (TAS) are the essential technologies to improve MRAM performence [2], [3]. The thermo-spin injection, converting heat current to spin current, will be a new source to reverse the magnetic momentum by thermal spin-transfer torques. [4] Both the TAS scheme and the thermal spin-transfer torques effects are related to the heating process in the magnetic tunneling junction (MTJ). Therefore, it is important to explore the production and transport of heat flow in MTJs. In most electronic systems, the Joule heating effect is the main contributor to heat in nanodevices [5]. Meanwhile, the tunneling spin scattering heating is another critical heating source caused by the inelastic scattering to excite magnons and phonons in MTJs. [6]. Sousa et al. once used a heat equation in 1D structure to simulate the heat process with the tunneling electron heating [7]. They reported the importance of tunneling spin scattering on the temperature profiles in the ferromagnetic layers. However, the temperature gradient, which is the source of the thermal spin injection, has not been considered seriously. Here, we systematically studied the temperature and temperature gradient induced by the tunneling spin scattering in MTJ using 3D numerical simulations.