We report the magnetism of a ferromagnetic two phase mixture system by investigating the microstructural evolution and relevant property changes as a function of alloy composition in CoFeSiB film. The crystal structure evolved from an amorphous to hcp Co nanocrystal embedded two-phase mixture when Co concentration exceeded the critical amount (∼75 at.%) confirmed through TEM and XRD. Very low coercivity value was observed in the amorphous samples. The soft magnetic properties are due to the fact that the magnetic moments of Co-rich phase are exchange-coupled via the amorphous matrix, as a consequence the magnetic anisotropies are averaged out in the amorphous system. Meanwhile, beyond 75 at.% of Co, an abrupt increase in coercivity was observed in the nanocrys- talline samples where highly anisotropic Co nanocrystals were precipitated. The hard magnetic properties resulted from the magnetic decoupling (breaking of the nanocrystal-amorphous matrix-nanocrystal coupling chain) because the exchange forces are not able to overcome the magnetocrystaline anisotropy. We also found that antiferromagnetic exchange coupling existed at the nanocrystal-amorphous matrix interfaces.
Bibliographical noteFunding Information:
This work was supported by the Korea Science and Engineering Foundation through the National Research Laboratory Program (No. M60501000045-05A0100-04510). B. S. Chun acknowledges financial support from by the Korea Research Foundation Grant (KRF-2006-352-D00091).
- Negative remanence
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Electrical and Electronic Engineering