The perpendicular shape anisotropy spin transfer torque magnetic random-access memory (PSA-STT-MRAM) is a recent concept proposed to maintain the thermal stability of standard MRAM at small diameters, considering thick vertical pillars as the free layer. To explore the specific physics of such systems with a three-dimensional nature, we have performed simulations combining a micromagnetic model coupled self-consistently with spin-dependent transport equations. The 3D shape induces flower states at the upper and lower surfaces. In addition, the fieldlike component of STT is found to be larger than in thin elements such as in standard MRAMs, suggesting that it needs to be considered. The combination of both effects leads to the efficient excitation of edge ferromagnetic resonance modes, playing a key role in magnetization reversal. These results highlight features of 3D nanomagnetic systems, largely disregarded so far. These must be considered to reliably describe PSA-STT-MRAM, but more broadly in the rising field of 3D nanomagnetism.

Close

PrevNext

View figure in article

• Magnetization switching
• Micromagnetism
• Spin accumulation
• Spin transfer torque