Hydrogen sorption property of magnesium (Mg) in the form of sandwiched Pd/Mg/Pd films is investigated. Pulsed laser deposition method was applied to deposit the samples consisting of films of nanoparticles. The enthalpy of formation of MgH(2) was found to be -68 kJ/mol H(2) for films with nanoparticle size on the order of 50 nm, which is smaller than the value for bulk MgH(2) and may be explained by the concept of excess volume. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.