Electrical nucleation and detection of single 360° homochiral Néel domain walls measured using the anomalous Nernst effect

Abstract

Using a thermoelectric measurement, we demonstrate the nucleation and detection of a single 360° homochiral Néel domain wall (DW), formed by an independently nucleated pair of 180° Néel DWs having the same helicity in a perpendicular magnetic anisotropy track. The DW formation is governed by strong interfacial Dzyaloshinskii-Moriya interaction (DMI) and detected at room temperature using the anomalous Nernst effect (ANE). A large DMI can be generated at an interface where the symmetry is broken between a material having a large spin-orbit coupling and a thin ferromagnetic layer. The ANE voltage, VANE∝∇T×M, is sensitive to the magnitude of the out-of-plane magnetization M through a confined in-plane temperature gradient ∇T and allows for the direct thermoelectrical detection of the DW position with nanoscale accuracy along the track. Here, we present evidence that independently nucleated pairs of 180° Néel DWs in microwire devices can be brought together by an applied magnetic field to form a 360° homochiral Néel DW. Subsequently, we show that a strong magnetic field needs to be applied in order to annihilate the 360° DW due to the strong interfacial DMI in our Pt/Co(0.6nm)/AlOx multilayers. In addition to enabling a high magnetic storage and data transfer rate with low power consumption in novel computational and storage devices, such DWs facilitate a reduction in bit size down to a few nanometers with metastability.