Orthogonal spin transfer MRAM

Spin-Transfer Magnetic Random Access Memory (ST-MRAM) devices hold great promise as a universal memory [Katine 2008]. ST-MRAM is non-volatile, has a small cell size, high endurance and may match the speed of SRAM. A disadvantage of the common collinearly magnetized ST-MRAM is their non-deterministic switching process, which leads to long switching times and broad switching time distributions [Devolder 2008, Koch 2004]. This delay is due to the fact that the torque is zero if the layers are either parallel or antiparallel [Slonczewski 1996] and hence switching cannot be initiated by the torque alone. Typically the process is started by an initial misalignment of the free layer stemming from thermal excitations. Relying on thermal initiation leads to incoherent reversal with an unpredictable incubation delay in the ns range [Devolder 2008] and broad switching time distributions [Koch 2004].