Magnetic avalanches induced by magnetic sweep rate in a cluster glass

We study magnetic avalanches in La_1-xSr_xCoO₃ and show that we can induce these avalanches for certain magnetic field sweep rates. La_1-xSr_xCoO₃ with 0.1 ≤ x ≤ 0.15 are magnetic cluster glasses consisting of magnetic Co clusters seeded by Sr dopant atoms, surrounded by non-magnetic Co ions. For certain ranges of magnetic field sweep rates, large and random steps are observed in the magnetization, consistent with near-system-size magnetic avalanches. Beyond this range, magnetic field sweep rates produce smooth curves of magnetization vs magnetic field. We develop a model effectively showing that the magnetic interactions between the clusters are controlled by the magnetic field sweep rate.