Magnetization reversal and emergent magnetic monopole-like state in square artificial spin ice vertex with defects

We have investigated the micro-magnetic behavior as well as magnetization reversal of dipolar coupled magnetic nanoislands with strong shape anisotropy arranged in a square artificial spin ice geometry. Our 0 K-temperature simulation results show that metastable two-in two-out state is stabilized at remanence of regular configurations. A complex interplay of defects and dipolar interaction leads to a predictable three-in one-out or three-out one-in higher energy state. Switching of the magnetic states is defined by the reduction of the no. of high-energy head-to-head or tail-to tail magnetic state.