Coercive properties of Nd2 Fe14 B + Fe nanocrystalline composites exhibiting wide distributions of switching field in the frame of the global nucleation model

O. V. BILLONI; S. E. URRETA; L. M FABIETTI; H. BERTORELLO

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

ELSEVIER SCIENCE BV

Año: 2002 vol. 250 p. 179 - 189

0304-8853

The demagnetization processes in Nd2F14B+aFe nanocrystalline composites exhibiting square and two-stephysteresis loops are investigated. In all these microstructures, an expanding nucleus model (Global Model) reasonablydescribes the experimental results in the entire range of the demagnetization loop, provided different sites acting asinverse nucleus are considered. Nucleation is found to take place in both phases and under different coupling conditionsexhibiting, in each case, a different reversion regime. Each regime has associated definite values of specific nucleussurface energy and effective local demagnetizing factor, which are similar in all the specimens, in spite of their differentmicrostructures and compositions. These specific surface energy values are close to those expected for domain wall-likeconfigurations resulting from competing interactions in the particular nucleation site, not always related to the intrinsicproperties of the phase itself but largely determined by inter-grain interactions.