Iron nanoclusters have been deposited by the gas-phase aggregation technique to form multilayered structures with outstanding exchange-bias (H-E) values up to H-E = 3300 Oe at low temperatures. In order to explain the observed magnetic properties, composition and crystallographic phase have been determined by X-ray absorption spectroscopy. A metal-oxide core-shell arrangement has to be discarded to explain the large obtained values of H-E since structural results show nanoclusters formed by the antiferromagnetic alpha-Fe2O3 oxide. Moreover, nanoparticles of few nanometers formed by substoichiometric alpha-Fe2O3 explain the observed weak ferromagnetism and let to understand the origin of large exchange bias by the interaction between different spin sublattice configurations provided by the low iron coordination at surface. (c) 2011 Elsevier B.V. All rights reserved.