Beating micromagnetic limits on skyrmion stability by long-range frustration

Abstract: Skyrmion stability is commonly assumed to scale with skyrmion size or exchange stiffness within micromagnetic models. Here, we demonstrate that long-range exchange frustration can break this paradigm, enhancing the collapse energy barrier without increasing skyrmion size or magnetic energy scale. By mapping the continuum model onto a spin-lattice Hamiltonian, we find that skyrmions with identical micromagnetic parameters can exhibit significantly different energy barriers, depending on their underlying atomistic exchange interactions. We attribute this behavior to saddle point textures, whose pronounced noncollinearity captures long-range frustration beyond the micromagnetic approximation. We further develop an exchange optimization framework to predict that long-range frustration can double the energy barrier in physically realistic conditions, possibly valid for ultrathin films or van der Waals magnets. These results hold across different lattice symmetries, revealing an intrinsic limitation of micromagnetics and establishing long-range frustration engineering as a promising route toward highly stable nanoscale skyrmions.