Terahertz magnetic susceptibility of pyramid-shaped L10-FePt nanodot arrays

Understanding the magnetic states and their dynamics in patterned ferromagnetic materials is of great importance for ultrahigh-density recording from the viewpoints of both fundamental research and practical applications. However, reliable access to magnetization dynamics in magnetic materials and devices on the technologically highly relevant terahertz range remains challenging. Currently, there is a lack of reports on terahertz magnetic susceptibility. Here, through micromagnetic simulations, we study the dynamics of pyramid-shaped, isolated magnetic nanodots and their arrays made of L1(0)-FePt with high magnetocrystalline anisotropy. Numerical results reveal a significant magnetic response of isolated pyramid nanodots in the terahertz range. Specifically, two resonant modes, namely, a bulk mode and an edge mode, have been identified. For the lateral size above similar to 100 nm, the nanodot's bulk mode splits and higher-order modes appear. Furthermore, the calculated spatial Fourier amplitude of resonant modes of nanopyramid arrays exhibits the dependence of lateral size and inter-dot spacing. These findings are expected to open up a promising route to terahertz spintronics utilizing magnetic nanostructures.