Visualization of Spontaneous Domain Wall Fluctuation in Artificial Spin Ice using Bragg Coherent Diffraction Imaging (BCDI)*

Inhomogeneity caused by a defect is known to play an important role in the emergence of long-range order and phase stability in strongly correlated systems. But their role in an artificial mesoscopic system is not very well understood. We studied spontaneous domain wall fluctuations in a dipolar-coupled antiferromagnetic (AF) artificial lattice for a wide temperature range by introducing defects to the magnetic lattice. BCDI reconstruction was performed using speckles under the half-integer AF peaks, revealing seconds-to-milliseconds timescale nucleation and annihilation of single domain wall. Our result shows that BCDI is an effective method of measuring fast fluctuation in the vicinity of a phase transition.