Opening the Neuromorphic Design Space—Engineering Spin Crossover Devices with Compositionally Complex Oxides

We have recently demonstrated the utility of spin crossover oxides, such as LaCoO₃, in various computational paradigms including axon-like signal transmission[1] and true random number generation[2]. However, the design space for electrothermally induced spin crossover devices is limited by conventional material constraints. Here, we explore expanding material candidates with oxides that can be engineered beyond traditional design limits through a focus on compositionally complex oxides. These materials, often called high entropy oxides, have lattice sites that share more than four cations, forming single-phase solid solutions with unique properties. For example, we demonstrate compositional complexity as a tunable parameter in the spin-transition oxide semiconductor La_1-x(Nd,Sm,Gd,Y)_x/4CoO₃, by varying the population x of rare earth cations over 0.00≤x≤0.80. Across the series, increasing complexity is revealed to systematically improve crystallinity, increase the amount of electron versus hole carriers, and tune the spin transition temperature and on-off ratio[3]. The unconventional properties that emerge and the potential to engineer such oxides into next generation computing devices will be discussed.
[1] T.D. Brown et. al. Nature, 2024
[2] K.S. Woo et. al. Nature Communications, 2024
[3] A. Zhang et. al. Advanced Materials, 2024