Observation of magnetic nanodomains in TmFeAl

The magnetic properties of TmFeAl and ErFeAl have been studied using neutron depolarization and diffraction. The first compound exhibits an extended first order magnetic transition between 10 and 60 K and its ordered state consists of magnetic nanodomains. Neutron depolarization displays the formation and growth of small magnetic domains as the temperature decreases. The average domain size is clearly smaller than 30 nm at 4 K and the existence of magnetic nanodomains is confirmed with neutron diffraction. The magnetic properties of ErFeAl do not display this anomalous behaviour but show a magnetic domain size of 0.4 μm. The structural disorder of the Fe atoms in the lattice combined with the high anisotropy of the Tm moments gives rise to the observed magnetic behaviour.