Magnetic Monopole Noise on Octahedral Spin Ice

One of the most salient features of spin ice systems are emergent quasiparticle excitations that take the form of magnetic monopoles. The peculiar nature of these excitations reflects in many of their unusual properties, from thermodynamic quantities like the heat capacity to response and out of equilibrium properties like the susceptibility and magnetic avalanches. Recent SQUID measurements highlighted a further connection between the monopole excitations and the magnetic noise in these materials, exhibiting an anomalous power law behaviour that remains hitherto poorly understood. Here we consider a frustrated spin ice-like system , which we call octahedral spin ice (OSI), consisting of antiferromagnetically interacting Ising spins forming corner sharing octahedra. Using a combination of Monte Carlo simulations and effective modelling, we investigate how the creation, annihilation and propagation of the excitations in OSI contribute to the magnetic noise spectrum, shedding light on different factors that affect its anomalous behaviour in these materials.