Simulation of multilevel cell spin transfer switching in a full-Heusler alloy spin-valve nanopillar

A multilevel cell spin transfer switching process in a full-Heusler Co ₂FeAl_0.5Si_0.5 alloy spin-valve nanopillar was investigated using micromagnetic simulations. An intermediate state of two-step spin transfer magnetization switching was reported due to the four-fold magnetocrystalline anisotropy; however, we discovered the intermediate state has two possible directions of -90° and +90°, which could not be detected in the experiments due to the same resistance of the -90° state and the +90° state. The domain structures were analyzed to determine the mechanism of domain wall motion and magnetization switching under a large current. Based on two intermediate states, we reported a multilevel bit spin transfer multi-step magnetization switching by changing the magnetic anisotropy in a full-Heusler alloy nanopillar.