Heterostructures for exploring altermagnetic and superconducting spintronics

• Applicants: Professor Jairo Sinova, Ph.D.; Dr. Libor Smejkal; Privatdozent Dr. Andy Thomas
• Subject Area: Experimental Condensed Matter Physics ; Theoretical Condensed Matter Physics
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 545503637

Altermagnetism describes a symmetry class of compensated magnets in which the spin symmetry group to which they belong allows for alternating spin polarizations both in the crystal space and in the momentum space of the non-relativistic electronic structure. Altermagnets combine merits of ferromagnets, like magnetoresistance and spin torque effects, and merits of antiferromagnets, like zero net magnetization and THz dynamics, that were regarded as principally incompatible. They also have merits unparalleled in either of the above-mentioned two traditional basic magnetic phases: like the unconventional spin splitter effect and the ability to host spin-polarized triplet-superconductivity. The actual development of a new avenue in spintronics, using altermagnetism, now calls for the more direct demonstration and detailed understanding of more core spin-physics effects, and in more materials, so far, among four altermagnets experimentally demonstrated: RuO2, MnTe, Mn5Si3, CrSb. Not only is the choice of altermagnetic material relevant, but the choice of other materials and optimization of the interfaces that make up the heterostructures are essential to take advantage of the spin polarization of altermagnets. This project will demonstrate core spin-physics associated with the ability of altermagnets to display no net magnetization and yet some spin polarization. A key focus hereby will be on the experimental observation of the tunnel magnetoresistance and spin transfer torque effects, as well as spin polarized triplet-superconductivity, and their theoretical modelling in actual heterostructures. We will use Mn-based materials such as Mn5Si3, and MnTe as model material system, embedded in ad hoc heterostructures. The major advantage of our consortium lies in the fact that we are the only ones to date to have mastered the growth of altermagnetic Mn5Si3, and subsequently demonstrated and manipulated its altermagnetic character, using its magneto-thermo-electrical properties. Building on this breakthrough is a key drive of the present proposal, as it now allows us to further explore spin polarization for altermagnetic spintronics, using ad hoc heterostructures. The partnership between two German (IFW and JGU) and two French laboratories (SPINTEC and CINaM) brings along a unique combination of know-how and experimental capabilities to study dedicated samples with different approaches – high quality thin film deposition, nanofabrication, superconductivity, magneto-transport based on tunnel magnetoresistance and spin torque manipulation, and different material-specific theoretical modelling methodology.

• DFG Programme: Research Grants
• International Connection: France
• Partner Organisation: Agence Nationale de la Recherche / The French National Research Agency
• Cooperation Partners: Professor Dr. Vincent Baltz; Professorin Dr. Lisa Michez