Dual referenced composite free layer design optimization for improving switching efficiency of spin-transfer torque RAM

Abstract

We present a detailed numerical analysis of switching efficiency for the recently proposed dual referenced composite free layer structure with respect to Gilbert damping. Low anisotropy assistive layers enable reduction of Gilbert damping and an increase of partial spin polarization within those low anisotropy layers—not feasible with single layer structures that require high anisotropy for thermal stability. When the damping of the soft layers is ultra-low, an efficiency (kBT/μA) of 8.1 is achieved for the composite structure with perpendicular anisotropy. This represents an improvement of 286% and 913% relative to the state-of-the-art dual-referenced and conventional STT-RAM cells, respectively. Results for structures with longitudinal anisotropy are also presented. A linear calculation of the STT polarization pre-factor is also described that captures all reflections.

Field- and temperature-modulated spin diode effect in a GMR nanowire with dipolar coupling

“…The above equation, together with the equations ( 17) and ( 15) for δθ, δφ, δΛ, and δΩ, is sufficient to find the spin diode signal (16). Since the solution for spin diode signal includes the dynamical matrix X, the V DC signal can be enhanced when the driving force (represented by the vector Y) matches the natural frequencies calculated from equation ( 13)…”

“…14 Nevertheless, most of these devices with multiple free magnetic layers, still include at least one, usually thick, pinned magnetic polarizer. 15,16 Regardless of its source, the coupling between layers may lead, in general, to more complex magnetization dynamics and a non-trivial behaviour of the device. Therefore, it is important to have a theoretical description in order to understand the experimentally measured characteristics of these devices.…”

“…Moreover, they were also dynamically coupled by spin transfer torque (STT) effects [14]. Nevertheless, most of these devices with multiple free magnetic layers, still included at least one, usually thick, pinned magnetic polarizer [15,16].…”

Interaction of two domain walls during spin-torque-induced coherent motion

“…The effects of spin transport in inhomogeneous magnetic systems have important implications for both the understanding of fundamental physics and the development of potential applications. Electrical generation of spin torque, which is a direct manifestation of the conservation of the angular momentum associated with spin, permits fast, localized electrical switching of magnetic domains [1][2][3][4], electrical driving of ferromagnetic resonance [5][6][7][8][9], and controlled generation of coherent magnons [10,11]. The study of the motion of domain walls induced by this spin torque [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] may lead to novel spin torque devices [32][33][34][35][36][37][38].…”