Almost everyone is familiar with the phenomenon of refrigerator magnets that lose their magnetization over time and simply fall off. The fact that the "adhesive force" of the magnets can be restored by bringing the magnet near another, still magnetized magnet, is one of the first things taught to students about magnetism and an everyday example of the behavior of ferromagnetic materials in a magnetic field. This so-called hysteresis behavior also includes the ability to "reverse" the magnetization of the ferromagnetic material by changing the direction of the applied magnetic field. This process is one of the most important technological applications of magnetic materials, ranging from magnetic storage media to switching elements in microelectronics.

In this magnetization reversal, there is a point at which the magnetization becomes zero before it changes direction. This state is typically described by the occurrence of macro- or microscopic domains in the magnetic material whose magnetizations point in different directions, so they cancel each other out and the overall magnetization disappears.

In their recently published article in "Nature Communications" titled "Magnetization reversal through an antiferromagnetic state," a group of Augsburg scientists led by Dr. Somnath Ghara and Dr. Joachim Deisenhofer (from the research group of Prof. Istvan Kezsmarki) along with colleagues from Groningen, demonstrated that this standard picture of magnetization reversal, achieved through the compensation of domains at a macro- or microscopic scale, does not apply to all materials and needs to be expanded. The researchers combined measurements of magnetization, electric polarization, optical properties in the THz frequency range, and theoretical simulations to find out that the magnetization reversal in the polar magnet (Fe:Zn)₂Mo₃O₈ occurs through an antiferromagnetic state, i.e., a state where the compensation of magnetization occurs not just on a macro- or microscopic scale but at the atomic level. These quantum materials are also at the core of the new Transregional Collaborative Research Center TRR360, approved by the German Research Foundation, led by the University of Augsburg and TU Munich.

This discovery is not only remarkable from the standpoint of basic research in the field of magnetization phenomena, but it also opens up new perspectives in the area of controlling magnetization on the smallest scales, thus offering great potential for the development of much smaller electronic components for the electronics of the future. The fact that the characteristic optical excitations of the material lie in the THz frequency range also opens up additional possibilities for extremely fast switching processes in the field of spintronics.

Publication:
Ghara, S., Barts, E., Vasin, K. et al. Magnetization reversal through an antiferromagnetic state. Nat Commun 14, 5174 (2023). https://doi.org/10.1038/s41467-023-40722-y