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

TL;DR

This paper demonstrates the first real-space imaging of non-collinear antiferromagnetic order in a thin film using a single NV magnetometer, revealing nanoscale spin textures and electric-field control at room temperature.

Contribution

It introduces a non-invasive NV-based scanning magnetometry technique to visualize complex antiferromagnetic order in thin films at room temperature, enabling nanoscale control and imaging.

Findings

Imaged the spin cycloid in BiFeO₃ with a period of ~70 nm.

Demonstrated electric-field manipulation of the antiferromagnetic order.

Validated NV magnetometry as a tool for complex magnetic order imaging.

Abstract

While ferromagnets are at the heart of daily life applications, their large magnetization and resulting energy cost for switching bring into question their suitability for reliable low-power spintronic devices. Non-collinear antiferromagnetic systems do not suffer from this problem and often possess remarkable extra functionalities: non-collinear spin order may break space-inversion symmetry and thus allow electric-field control of magnetism, or produce emergent spin-orbit effects, which enable efficient spin-charge interconversion. To harness these unique 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 nanomagnetometer based on a single nitrogen-vacancy (NV) defect in diamond, we demonstrate the first real-space visualization of non-collinear antiferromagnetic order in a magnetic thin film, at room temperature. We image the spin cycloid of a multiferroic BiFeO$_3$ thin film and extract a period of $\sim70$ nm, consistent with values determined by macroscopic diffraction. In addition, we take advantage of the magnetoelectric coupling present in BiFeO$_3$ to manipulate the cycloid propagation direction by an electric field. Besides highlighting the unique potential of NV magnetometry for imaging complex antiferromagnetic orders at the nanoscale, these results demonstrate how BiFeO$_3$ can be used as a versatile platform for the design of reconfigurable nanoscale spin textures.