Transferred hyperfine fields in magnetic amorphous alloys

A¹¹B-NMR study of the amorphous systems Fe80-xNixB20and Fe80-xCOxB20at room temperature and 77 K has been undertaken. Relatively broad hyperfine field distributions HFFD have been obtained, with a relative width (where M1and M2are the first and second moment of HFFD) increasing from 20% for Fe80B20to about 65% for Fe20Ni60B20and about 80% for CO80B20. The average hyperfine field scales with the average moment of the alloys. The transferred hyperfine field at¹¹B seems to originate from the conduction electron polarization induced by the magnetically ordered transition metal atoms. Emphasis was put on the study of spin-lattice and spin-spin relaxation times T1and T2as functions of composition and in the latter case on its dependence on frequency.