Zhewen Xu

Research project

Skyrmions: Imaging and Characterization at Ambient Conditions via Scanning NV Magnetometry

Project supervisor

Dr. Gabriel Puebla-Hellman

Recruitment date

Zhewen Xu

Hi, this is Zhewen Xu. He is from the east of China.

He is a master student who is majored in Materials Science in RWTH Aachen, Germany. After completing his master project in the area of anomalous Hall effect, spin-orbit torques and Dzyaloshinskii-Moriya interaction, he found that he was enchanted by this topological interpreted scientific world as well as complex magnetic textures. Gradually, he became ‘greedy and greedy’. Simulation work was not able to satisfy him. He deeply knew that he was supposed to manipulate spins in the real world and see the complex magnetic textures with his own eyes. Therefore, he made up his mind in continuing his PhD work in this field.

SPEAR perfectly combines his strengths (solid theoretical knowledge in topological theory as well as antisymmetric exchange) and his aspirations (to witness all these fascinating physic properties in real word), without hesitation he applied for this program. Additional benefits, such as secondment, frequent interactions with other elite researchers from other prestigious universities, institutes and companies all over the world, also contribute a lot to his decision on this program.

In spare time, he enjoys reading books on psychology and economics. Classic rock and roll together with jazz is also his favourites.

Project Description

Magnetic skyrmions are quasiparticles with a wide range of interesting and non-trivial physical properties. In addition, the recent emergence of materials that support skyrmions at room temperature adds potential industrial applications for low power random access memories. They remain, however, difficult to characterize and image.

A suitable tool for the study of skyrmions is scanning Nitrogen Vacancy (NV) magnetometry. By scanning a single NV, essentially an atomic size magnetic sensor, in close proximity over the sample, we map the sample's magnetic field with nanoscale resolution at ambient conditions and without disturbing the sample.

Skyrmions are typically very small magnetic features, close to the resolution limit of scanning NV. Improving the minimum feature size that our method can detect is the primary goal of the project. Reducing the distance between the sample and the NV is the obvious approach, as the resolution is proportional to the sample-NV distance. This implies moving the NV closer to scanning tip surface, which increases the NV-surface interaction and creates a multi-faceted project with elements of material engineering, nanoscale fabrication and quantum measurements coming together to create the next generations of high resolution, high signal-to-noise scanning probes.

Scanning NV provides a wealth of data about the magnetic sample, ranging from magnetic field magnitude to topology. By moving to scanning tips with several NVs, we can obtain additional vector information, which is especially useful for non-flat samples. Fabricating such probes, creating the necessary read-out schemes and demonstrating this on actual samples is a second part of this project.

Host institution

At QZabre, everything revolves around imaging magnetic fields at the nanometer scale using quantum sensing. We are an ETH Spin-off founded in 2018 with the goal of making scanning Nitrogen Vacancy magnetometry as easy as atomic force microscopy. Our product portfolio contains both state-of-the-art single NV scanning probes as well as a full turnkey, high performance instrument. Our team of eight scientists and programmers fully focuses on pushing the boundaries of nanometer scale magnetic characterization technology.

Prof. Christian Degen, who is one of the pioneers of NV magnetometry, will support the project. His Spin Physics group at the Swiss Federal Institute of Technology Zurich (ETHZ) is at the forefront of magnetic imaging, both at ambient as well as cryogenic conditions.

Planned Secondments

UHAM (Hamburg, Germany), under the supervision of Kirsten von Bergmann.

Registering University

ETHZ (Zurich, Switzerland).

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