Observation of magnetic nanodomains in TmFeAl

The magnetic properties of TmFeAl and ErFeAl have been studied using neutro n depolarization and diffraction. The first compound exhibits an extended f irst order magnetic transition between 10 and 60 K and its ordered state co nsists of magnetic nanodomains. Neutron depolarization displays the formati on and growth of small magnetic domains as the temperature decreases. The a verage domain size is clearly smaller than 30 nm at 4 K and the existence o f magnetic nanodomains is confirmed with neutron diffraction. The magnetic properties of ErFeAl do not display this anomalous behaviour but show a mag netic domain size of 0.4 mu m. The structural disorder of the Fe atoms in t he lattice combined with the high anisotropy of the Tm moments gives rise t o the observed magnetic behaviour. (C) 2000 Elsevier Science S.A. All right s reserved.