Time resolved diamond magnetic microscopy of single transition metal magnetic nanoparticles

Understanding the magnetic properties of small transition metal magnetic nanoparticles (TMMNPs) can help in exploiting their useful properties such as high surface-to-volume ratio and tailorable surface chemistry for applications in catalysis, biosensing, and ultra-high-density magnetic recording. At size below 10 nm, surface effects play a major role in determining their magnetic properties. Symmetry breaking of the crystal structure at the particle surface, dangling bonds, and surface strain can alter their properties. Accurate measurements of magnetic properties of single TMMNPs would therefore shed light on their critical properties. However, measuring these properties of such small particles at ambient conditions presents a great challenge due to the lack of sensitivity of current nonperturbative magnetic imaging techniques. Here we show recent measurements using magnetic microscopy based on nitrogen vacancy centers in diamond to measure the static and dynamic magnetic properties of individual 2-10 nm TMMNP (CoPt and FePt). Histograms of critical parameters such as magnetic anisotropy, saturation magnetization, and magnetic relaxation are extracted and correlated with morphology data taken by AFM, SEM, and TEM.