Observation of the exchange spring behavior in hard-soft-ferrite nanocomposite

Nanocomposite of hard (BaFe12O19) and soft ferrite (Ni0.8Zn0.2Fe2O4) are prepared by the mixing of the individual ferrite components at appropriate ratio and subsequent heat treatment. Initially the microstructure of the individual phases is controlled by suitable processing. We have observed the exchange spring behavior in the soft-hard ferrite composite for the first time by tailoring the particle size of the individual phases and by suitable thermal treatment of the composite. It is found that the exchange interaction dominates over the dipolar interaction for smaller particle sizes of the soft ferrite. The magnetization of the composite showed hysteresis loop that is characteristic of the exchange spring system. This gives experimental proof for some theoretical modeling as well as paves way for developing magnet with higher (BH) max product based on ferrites. (c) 2008 Elsevier B. V. All rights reserved.