C. Echevarria-Bonet, D. P. Rojas, J. I. Espeso, J. Rodríguez Fernández, L. Rodríguez Fernandez, P. Gorria. A. Blanco, M. L. Fdez-Gubieda, E. Bauer, G. André, and L. Fernandez Barquín
An unusual 4f-superantiferromagnetic state characterized by simultaneous antiferromagnetic and spin-glass behaviors induced by particle-size reduction is revealed in metallic nanoparticles (≈9 nm) of TbCu2. The Néel temperature is 46 K and the glassy freezing is below ≈9 K and governed by a critical slowing down process. Neutron diffraction at 1.8 K establishes the superantiferromagnetism. The latter is settled by the nanoparticle moments and the freezing mechanism is provided by the surface spins.