FE-57 MOSSBAUER-EFFECT STUDY OF ND-(FE, CR)-B PERMANENT MAGNETIC-MATERIALS

The alloys Nd16Fe76-xCrxB8, with x = 0, 3, 5, and 7, were prepared by induction melting technique. The x-ray powder diffractograms show that all the samples crystallized in tetragonal Nd2Fe14B phase along with NdFe4B4 as a secondary phase. The lattice parameters are found to decr ease with Cr concentration. The Curie temperature, determined by the d ifferential scanning calorimetry technique, decreases with Cr concentr ation at the rate of 7.4 K/at. % Cr. The Mossbauer study clearly shows that Cr has a strong preference for the j(2) site; the weighted avera ge hyperfine magnetic field decreases by 40 kOe when an Fe atom in the Nd2Fe14B formula unit is replaced by a Cr atom. Cr substitution decre ases the transferred hyperfine magnetic field at the Fe sites and also the Fe-magnetic moment. (C) 1998 American Institute of Physics. [S002 1-8979(98)06118-0].