Interface control of the magnetic chirality in CoFeB|MgO heterosctructures with heavy metal underlayers

摘要

Recent advances in the understanding of spin orbital effects in ultrathinmagnetic heterostructures have opened new paradigms to control magnetic momentselectrically. The Dzyaloshinskii-Moriya interaction (DMI) is said to play a keyrole in forming a Neel-type domain wall that can be driven by the spin Halltorque, a torque resulting from the spin current generated in a neighboringnon-magnetic layer via the spin Hall effect. Here we show that the strength andsign of the DMI can be changed by modifying the adjacent heavy metal underlayer(X) in perpendicularly magnetized X|CoFeB|MgO heterstructures. Albeit the samespin Hall angle, a domain wall moves along or against the electron flowdepending on the underlayer. We find that the sense of rotation of a domainwall spiral11 is reversed when the underlayer is changed from Hf to W and thestrength of DMI varies as the number of 5d electrons of the heavy metal layerchanges. The DMI can even be tuned by adding nitrogen to the underlayer, thusallowing interface engineering of the magnetic texture in ultrathin magneticheterostructures.