Thermally induced dynamics in ultrathin magnetic tunnel junctions

Abstract

We consider the magnetization dynamics induced by thermally induced spin transfer torques in thin Fe|MgO|Fe tunnel junctions. The magnetization dynamics is described by the Landau-Lifshitz-Gilbert equation, including the thermal torques as computed from first principles. We show that the angular skewness of the torques importantly modifies the dynamics, e.g., leading to different instability criteria.

Enhanced thermal spin transfer in MgO-based double-barrier tunnel junctions

“…We plot the results in figure 2(a) in S1/S2 structure. At both peaks, t v in S2 structure is almost double larger than that in S1 structure due to the double spin transfer process existed in S2 structure, as expressed in equation (2). Both the two peaks contribute to room temperature TST torque.…”

“…Therein, the magnetization dependent parameter Q is the key to equation (1), which is well-studied by spin pumping theory [31,32]. By putting TST torque into the phenomenological LLG equation [2], one can estimate thermal induced magnetic dynamics.…”

“…At the same time, Λ in both S1 and S2 are smaller than that 3.5 in clean Fe | MgO(3)| Fe SBMTJs. It is rather interesting because the larger T T companied with smaller Λ would favor the magnetization switching in DBMTJs than SBMTJs [2]. The out-of-plane part of TST torque (T T ) is about 10% of T T , and we neglectT T in magnetic dynamic simulations.…”

“…To achieve TST torque (also called thermal torque) comparable to that induced by an electric bias, a large temperature gradient across magnetic elements should be established. Marked TST effect is first reported in a MgO-based magnetic tunnel junctions (MTJs) with ultra-thin barrier [2,3]. Therein, the skewed TST torque is more favorable to magnetic oscillation rather than switching, a temperature gradient D » T 60 K with  » T 100 K nm −1 is predicted to be needed to switch the magnetic configurations circularly, which is beyond the current experimental capability.…”

“…Switching the magnetic order parameter thermally is the basis for spin caloritronic applications such as logic devices and memories [1]. As a easy, efficient, and 'green' method to manipulate the magnetic order parameter, thermal spin transfer (TST) torque has received much attention recently [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. To achieve TST torque (also called thermal torque) comparable to that induced by an electric bias, a large temperature gradient across magnetic elements should be established.…”