Dysprosium nanoparticles synthesized by alkalide reduction

Abstract

Dy nanoparticles have been produced at subambient temperature by alkalide reduction. In the bulk, Dy is ferromagnetic below 89 K. In contrast, the nanoparticles’ magnetization is blocked below ∼9 and ∼20 K for unheated and samples annealed at 1000 °C for 4 h, respectively. This behavior is consistent with a reduction in T_c due to finite size effects. Magnetization is linearly dependent on field at temperatures higher than ∼6 times T_B and shows remanence-free hysteresis at lower temperature. Magnetic entropy curves generated from magnetization data are consistent with that expected for a paramagnet, yielding large values at low temperature due to the high effective moment of Dy.