Antibonding and Electronic Instabilities in GdRu2X2 (X = Si, Ge, Sn): A New Pathway Toward Developing Centrosymmetric Skyrmion Materials

Abstract: Chemical bonding is key to unlocking the potential of magnetic materials for future information technology. Magnetic skyrmions are topologically protected nano-sized spin textures that can enable high-density low-power spin-based electronics. Despite increasing interest in the discovery of new skyrmion hosts and their characterization, the electronic origins of the skyrmion formation remain unknown. Here, we study GdRu2X2 (X = Si, Ge, Sn) as a model system to study the connection among chemical bonding, electronic instability, and the critical temperature and magnetic field at which skyrmions evolve. The nature of the electronic structure of GdRu2X2 is characterized by chemical bonding, Fermi surface analysis, and density of energy function. As X-p orbitals become more extended from Si-3p to Ge-4p and Sn-5p, improved interactions between the Gd spins and the [Ru2X2] conduction layer and increased destabilizing energy contributions are obtained. GdRu2Si2 possesses a Fermi surface nesting (FSN) vector [Q = (q, 0, 0)], whereas GdRu2Ge2 displays two inequivalent FSN vectors [Q = (q, 0, 0); QA = (q, q, 0)] and GdRu2Sn2 features multiple Q vectors. In addition, competing ferromagnetic and antiferromagnetic exchange interactions in the Gd plane become more pronounced as a function of X. These results reveal some correlation among the electronic instability, the competing interaction strength, and the temperature and magnetic field conditions at which the skyrmions emerge. This work demonstrates how chemical bonding and electronic structure enable a new framework for understanding and developing skyrmions under desired conditions that would otherwise be impossible.