Magnetic phase diagram of Fe and Ni from crystals to amorphous structures

Magnetic properties of Fe and Ni have been investigated on the basis of the theory of metallic magnetism which interpolates between crystals and amorphous structures using the average coordination number z* and the fluctuation of interatomic distance Delta. Calculated magnetic phase diagram of Fe is shown to consist of three phases on the z* - Delta plane: the ferromagnetism (F) in the region z* less than or similar to 10.5, the spin glass (SG) in the region z* greater than or similar to 10.5, and the paramagnetism (P) around z* = 11.0 and Delta = 0.0. In the region F, the magnetization and the Curie temperature are weakened with increasing z(*), while they are considerably enhanced with increasing Delta. The phase diagram explains the ferromagnetism of amorphous Fe powder and the SG in amorphous Fe containing early transition metals. In the case of Ni, F and P are found. In the region F the magnetization first decreases and tends to become constant with increasing Delta. The Curie temperature also decreases but shows a minimum as a function of Delta. Both of them are found to be smaller than those of fcc Ni, and to be sensitive to the degree of structural disorder. This explains qualitatively the nonunique magnetism of amorphous Ni in experiment. (C) 1999 American Institute of Physics. [S0021-8979(99)06618-9].