Real-space imaging of non-collinear antiferromagnetic order with a single-spin magnetometer

Abstract

Although ferromagnets have many applications, their large magnetization and the resulting energy cost for switching magnetic moments bring into question their suitability for reliable low-power spintronic devices. Non-collinear antiferromagnetic systems do not suffer from this problem, and often have extra functionalities: non-collinear spin order may break space-inversion symmetry and thus allow electric-field control of magnetism, or may produce emergent spin-orbit effects that enable efficient spin-charge interconversion. To harness these traits for next-generation spintronics, the nanoscale control and imaging capabilities that are now routine for ferromagnets must be developed for antiferromagnetic systems. Here, using a non-invasive, scanning single-spin magnetometer based on a nitrogen-vacancy defect in diamond, we demonstrate real-space visualization of non-collinear antiferromagnetic order in a magnetic thin film at room temperature. We image the spin cycloid of a multiferroic bismuth ferrite (BiFeO) thin film and extract a period of about 70 nanometres, consistent with values determined by macroscopic diffraction. In addition, we take advantage of the magnetoelectric coupling present in BiFeO to manipulate the cycloid propagation direction by an electric field. Besides highlighting the potential of nitrogen-vacancy magnetometry for imaging complex antiferromagnetic orders at the nanoscale, these results demonstrate how BiFeO can be used in the design of reconfigurable nanoscale spin textures.

Antiferromagnetic spintronics

“…Direct observation usually requires large scale facilities with element-sensitive techniques like x-ray absorption spectroscopy (Weber et al, 2003;Salazar-Alvarez et al, 2009;Wu et al, 2011) or specific techniques with local probes like spin-polarized scanning tunneling microscopy (Bode et al, 2006;Loth et al, 2012) and quantum sensing with single spins (nitrogen vacancies) in diamond (Gross et al, 2017;Kosub et al, 2017). Alternatively, some information about antiferromagnetic domains can be inferred using indirect transport measurements.…”

Overcoming the Limits of the Interfacial Dzyaloshinskii–Moriya Interaction by Antiferromagnetic Order in Multiferroic Heterostructures

“…Very recently, a technique of scanning tunneling microscopy by a single nitrogen‐vacancy (NV) defect in diamond is used to image non‐collinear antiferromagnetic order in real space. [ 43 ] In future, this technique could be employed for direct observation of small size skyrmions at low temperature.…”

Micromagnetic modeling and imaging of vortex|meron structures in an oxide|metal heterostructure

“…For diamond N-V centre microscopy, a first set of images were produced without bias magnetic field, assuming that the signal is proportional to the magnitude of the projection of the stray magnetic field along the direction of the defect, which was aligned with the [111] crystallographic direction of the diamond [22,23]. The [001] and [110] crystallographic directions of the diamond were aligned along the z and x axes, respectively.…”