Researchers at the UAB, ICMAB and the ALBA Synchrotron, in collaboration with the UB and ICN2, have developed a new technique to locally modify the properties of a metamagnetic material. The method consists in applying local pressure to the surface of the material using nanometric needles and allows a much more easy and local modification than current methods. The research opens the door to a more accurate and precise control of magnetic materials and allows to improve the architecture and capacity of magnetic digital memories.
Some memory devices where information from smartphones and computers is stored are based on a very precise control of the magnetic properties, at nanoscopic scale. In certain cases, the combination of ferromagnetism (where the magnetism of all the atoms in the material points in the same direction) and antiferromagnetism (where it points alternately in opposite directions) is used to store the information. One of the materials that can show these two arrangements is the alloy of iron and rhodium (FeRh). This material presents a metamagnetic transition between these two phases at a temperature very close to room temperature, so that it can change state from antiferromagnetic to ferromagnetic simply when heated. The antiferromagnetic state is more robust and secure than the ferromagnetic one, since it is not easily altered by the presence of magnets in its proximity.
A team of researchers from the UAB, the ICMAB, and the ALBA Synchrotron, along with scientists from the UB and the ICN2 (Magnetic Nanostructures Group), have used mechanical pressure to modify this transition and stabilize the antiferromagnetic state. Pressing the surface of the iron-rhodium alloy with a nanometer-sized needle causes the magnetic state to change in a simple and localized way. By pressing on different areas of the material, the researchers have managed to generate antiferromagnetic nano-islands embedded in a ferromagnetic matrix, a very difficult task with the current techniques available. The new technique can allow the construction of magnetic nanometric devices with much smaller structures and much more robust and safe than the current ones, facilitating the manufacture of magnetic memories with different architectures that improve their capacities.
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Michael Foerster, Enric Menéndez, Emerson Coy, Alberto Quintana, Carles Gómez-Olivella, Daniel Esqué de los Ojos, Oriol Vallcorba, Carlos Frontera, Lucia Aballe, Josep Nogués, Jordi Sort and Ignasi Fina. Local manipulation of metamagnetism by strain nanopatterning, Materials Horizons (2020). https://doi.org/10.1039/D0MH00601G