Direct detection of neighboring stray field interaction on a single nanodisk using micro-focused Brillouin Light Scattering spectroscopy

Studying the effect of dipolar interaction between closely-packed nanodisks has become increasingly important in many applications such as high density information storage, magnonics crystals and spin torque oscillators. So far, these studies were focused on the collective magnetic behavior from an array rather than from a single disk under the influence of neighboring dipolar field. Recently, Keatley et al used a time-resolved scanning Kerr microscopy to isolate the dynamic dipolar interaction between a pair of nominally-shaped disks. However, a detailed scrutiny of phase-resolved Kerr ellipticity is required to determine, with limited accuracy, the dynamic dipolar coupling strength versus edge-to-edge spacing/diameter (s/d) ratio. In this work, we use a micro-focused Brillouin Light Scattering (μ-BLS) setup to systematically investigate the effect of increasing neighboring dipolar field on the dynamic behavior of a single nanodisk. Using pairs of identical disks with varying s, a direct detection of increasing neighboring dipolar field on a single disk is systematically performed. The influence of neighboring dipolar field in modifying the dynamic behavior of the resonance mode is evident in the measured spectra and the 2D mode profiles. In addition, by changing the relative orientation between the inter-disk coupling direction and the applied magnetic field (H_app) to be either parallel or perpendicular, different modes of dipolar interaction can be further distinguished.