MAGNETIC-PROPERTIES OF FE-CU-NB-SI-B NANOCRYSTALLINE MAGNETIC-ALLOYS

Several ribbons of composition Fe73.5Cu1Nb3Si16.5B6 and Fe73.5Cu1Nb3Si 13.5B9 were prepared by annealing the as-quenched samples between 525- degrees-C and 700-degrees-C, which induced nucleation of nanocrystalli tes of Fe bcc-type composition. Mean grain sizes were obtained from X- ray diffraction. Static magnetic properties were measured with both a Magnet Physik Hysteresis-Graph (up to 200 Oe) and a SHE S.Q.U.I.D. Mag netometer (up to 50 kOe). Soft magnetic parameters (coercive field and initial permeability) were very sensitive to grain size. The ZFC magn etization at low field showed a broad peak at a temperature T(M), thus signalling a certain distribution of nanocrystlline sizes, and T(M) s trongly decreased when the mean grain size decreased. Isothermal magne tization curves at low temperature showed the expected asymptotic beha vior of a random magnet material at low and high fields.