Fragility of the spin-glass-like collective state to a magnetic field in an interacting Fe-C nanoparticle system

The effect of applied magnetic fields on the collective nonequilibrium dynamics of a strongly interacting Fe-C nanoparticle system has been investigated. It is experimentally shown that the magnetic aging diminishes to finally disappear for fields of moderate strength. The field needed to remove the observable aging behavior increases with decreasing temperature. The same qualitative behavior is observed in an amorphous metallic spin glass $({\mathrm{Fe}}_{0.15}{\mathrm{Ni}}_{0.85}{)}_{75}{\mathrm{P}}_{16}{\mathrm{B}}_6{\mathrm{Al}}_3.$