Resilient spin dynamics in Y-doped TbSb near percolation limits

Understanding disorder in magnetic systems and designing materials with disorder resistant spinwaves is crucial for spintronics and magnonics. An effective model system for exploring magnetic disorder through non-magnetic element doping is hosted by cubic crystal structures like TbSb (S = 7/2, 9.7 μB). Y-doping in TbSb lowers the Néel temperature and allows for investigating the interplay between disorder and magnetic excitations across different doping concentrations. We examine the impact of Y-doping on magnetic excitations in TbSb using inelastic neutron scattering and SU(N) generalized spinwave modelling. With increasing Y concentration, magnons in TbSb gradually soften even upto its percolation threshold of 40% Y-doping. Surprisingly, magnons at 40% Y-doping survives even above the Néel temperature, even though it is expected to undergo paramagnon transition as in the case of pure TbSb. Simulations based on SU(N) generalized spinwave theory reveal how spin waves and crystal field excitations evolve with doping. Our study offers new insights into magnon behavior in disordered magnetic systems, emphasizing opportunities for deeper exploration in this field.