Reversible ion intercalation based tuning of magnetism in bulk ferromagnets

• Applicant: Professor Dr.-Ing. Horst Hahn, since 10/2017
• Subject Area: Synthesis and Properties of Functional Materials ; Experimental Condensed Matter Physics
• Term: from 2015 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 278066865

Aiming at superfast spintronics, electric-field control of magnetism is presently among the most thriving research areas. However, strong ferromagnets, typically being metallic in nature, can effectively screen the applied electric fields within a monolayer of surface atoms, thus limiting such effects to very small material volumes, adjacent to the surfaces/interfaces. Hence, in order to go beyond the interfacial magnetoelectric phenomena, here a concept of reversible ion-exchange mediated control of magnetization is proposed. The expected advantages are twofold; firstly, a complete on-and-off magnetism can be foreseen even for the strong ferromagnets; secondly, this approach would be pertinent to bulk material volumes. The idea stems from rechargeable batteries or pseudocapacitors where the reversible ion-exchange phenomena have been demonstrated for thousands of cycles; likewise, examples of reversible chemistry-controlled tuning of functional properties and its successful commercialization have been demonstrated, for example, in electrochromic devices. Here, in this proposed study we will concentrate on three different classes of magnetic materials with quite different magnetic interactions which will be tested - namely, super-exchange mediated ferrimagnets, materials with competing super and double exchange interactions and magnetic alloys with itinerant magnetism. The common goal in all the systems is to reversibly tune the valance state of the magnetic cations and thereby either balance the antiferromagnetically coupled magnetic sublattices in a ferrimagnetic system or trigger a magnetic phase transition between the competing magnetic states, in other systems. Being chemically-driven, the process would certainly be slower than the electric field-effect based devices; however, owing to the sheer strength of the controllable magnetic response, various possibilities for novel applications involving micromagnetic actuation can be anticipated; e.g. in microfluidics, or in sorting/guiding of magnetic species that can either be biological substances (cells, DNAs) or Janus particles designed for drug delivery.

• DFG Programme: Research Grants
• Cooperation Partners: Professor Dr. Helmut Ehrenberg; Professor Dr. Maximilian Fichtner; Professor Dr. Heiko Wende; Professor Dr. Wolfgang Wenzel
• Ehemaliger Antragsteller: Dr.-Ing. Subho Dasgupta, Ph.D., until 10/2017