Temperature dependent magnetic characterisation of core/shell Fe80Rh20 nanoparticles

Oxide free core-shell Fe80Rh20 nanoparticles with an average diameter of about 2 nm were wet-chemically synthesised with two different morphologies: either with Rh-rich or an Fe-rich core. The magnetic properties of these nanoparticles were investigated between 5 and 290 K by ferromagnetic resonance and superconducting quantum interference device magnetometry. The magnetic anisotropy field varied by a factor of 2 in this temperature range. The nanoparticles with Rh-rich core were found to have a higher anisotropy field of BA=0.214T at 5 K as compared to the nanoparticles with Fe-rich core (BA=0.169T). Multifrequency ferromagnetic resonance (4-24 GHz) was used to determine the g-factor. It was determined that the g-factor of nanoparticles with Fe-rich core is higher (g=2.08) compared to nanoparticles with Rh-rich core g=2.06, being close to the value for iron bulk.