Structural, magnetic and magnetostrictive behavior in Nd(Fe1-xCox)1.9 compounds

摘要

The crystal structure, magnetic properties and magnetostriction of polycrystalline magnetostrictive alloys Nd(Fe_1-xCo_x)_1.9 were investigated. It was found that the single cubic Laves phase can only be obtained in the samples with x>0.4 by a traditional annealing method. In contrast, the cubic Laves phase exists over the entire composition range studied in the samples annealed under high pressure. Both the Curie temperature and saturation magnetization increase with increasing Co concentration to a maximum at x = 0.2 and then decrease with further increasing x, which could be understood in the frame of rigid band model. The spin phase diagram for Nd(Fe_1-xCo_x)_1.9 is constructed to illustrate the arrangement for the easy magnetization direction and crystal structure. The magnetostriction of Nd(Fe_1-xCo_x)_1.9 increases with increasing Co concentration and peaks at x = 0.1 and then presents an anomalous behavior when 0.2≤x≤0.6. It is suggested that the external-field-induced lattice strain should be responsible for the anomalous magnetostrictive behavior.