Antiferromagnetic oxide materials offer the promise of advances in information technology and nanomedicine. In contrast to ferromagnetic materials, they are not affected by interference from external magnetic fields and could store data more permanently and reliably than is currently possible with magnetic materials. Oxide systems are thus of more interest than metallic ones, because they are easier to switch.
Magnetic states in an antiferromagnet
Unlike a ferromagnet, an antiferromagnet does not have a magnetic field that can be measured externally. Nevertheless, it is not considered to be a completely non-magnetic material. The spins of the electrons, however, are not aligned in parallel as in a ferromagnet, but in opposite directions. The magnetic moments therefore cancel each other out. Some members of the research team already presented their findings on the synthetically produced antiferromagnet now under investigation in a scientific publication in 2017. They showed that the material can be magnetised and reversed in polarity layer by layer by means of an external magnetic field – and therefore can be switched back and forth between different magnetic states in a controlled manner. Ferromagnetic manganate layers with a thickness of just a few nanometres are antiferromagnetically coupled to each other using ultra-thin, insulating titanium oxide layers. The polarisation direction of the spins reverses when transferred from one layer to the other.
Analysing the magnetic switching process with neutrons
The researchers from the JCNS and their colleagues from China, France, Switzerland and Great Britain have now identified the mechanism underlying the switching process. With the help of a polarised neutron reflectometry method, they succeeded in analysing the magnetic configuration of the layer system with microscopic resolution. In doing so, they found that magnetic solitons – boundary regions between two antiferromagnetically ordered zones that are vertically mobile – play an essential role in the process. These soliton waves also make it possible to transport data between the different layers of the system. The results thus indicate a path to the development of three-dimensional storage elements with high data density.
Original text: Angela Wenzik / JCNS
Original publication:
Soliton-Mediated Magnetic Reversal in an All-Oxide-Based Synthetic Antiferromagnetic Superlattice;
Kexuan Zhang, Kirill Zhernenkov, Thomas Saerbeck, Artur Glavic, Lili Qu, Christy J. Kinane, Andrew J. Caruana, Enda Hua, Guanyin Gao, Feng Jin, Binghui Ge, Feng Cheng, Sabine Pütter, Alexandros Koutsioubas, Stefan Mattauch, Thomas Brueckel, Yixi Su, Lingfei Wang, and Wenbin Wu;
ACS Applied Materials & Interfaces Article ASAP, DOI: 10.1021/acsami.1c02506
All-oxide-based synthetic antiferromagnets exhibiting layer-resolved magnetization reversal;
Binbin Chen, Haoran Xu, Chao Ma, Stefan Mattauch, Da Lan, Feng Jin, Zhuang Guo, Siyuan Wan, Pingfan Chen, Guanyin Gao, Feng Chen, Yixi Su, Wenbin Wu;
Science (published 14 July 2017), DOI: 10.1126/science.aak9717
Related News:
Article: “Science: Using Neutrons for Switchable Antiferromagnets”, Forschungszentrum Jülich from 14 July 2017: https://www.fzj.de/SharedDocs/Pressemitteilungen/UK/EN/notifications/2017-07-13-science-antiferromagnet.html;jsessionid=D99580CC63FD7D2E23CD4DAC9D3CB5E6
More information:
In addition to the MARIA instrument at the FRM II research neutron source, the scientists also carried out measurements at the British neutron source ISIS and the French neutron source ILL.