Magnetism and phase-transitional analysis of nano-metal gadolinium

The structures, grain sizes and magnetism were analyzed and computed for three typical samplesthe stock of polycrystalline metal Gd (sample 1), the bulk nanocrystalline Gd prepared by spark plasma sintering (SPS) technique and subjected to the annealing process of 623 K for 0.5 h (sample 2) and the bulk nanocrystalline Gd prepared by the SPS technique at 573 K (sample 3). The computation results indicated that the sample 3 had the efficiency of space filling up to 99.38%. The computation results of magnetization indicated that the ferromagnetism was contributed by the 4f7 electrons and 21% of the 5d1 itinerant electrons in the metal Gd. The ferromagnetism of the nanocrystalline Gd decreased significantly compared with the stock of the polycrystalline Gd. The possible reasons are: the existence of a small quantity of the Gd2O3 impurity, and the existence of the phase of antiferromagnetism in the nanocrystalline Gd. The curves of the magnetic susceptibility χ which are dependent on the temperature T of the samples were steep in the vicinity of the phase-transition point Tc. It was determined to be a second-order phase transition by the linear relationship between the reciprocal of the magnetic susceptibility 1/χ and temperature T by the analysis of Landau's phase-transition theory.