MICROSTRUCTURE OF CARBIDE-DISPERSED NANOCRYSTALLINE FE-TA-C FILMS

Nanocrystalline structure of soft magnetic Fe-Ta-C films crystallized from an amorphous state has been investigated. High-resolution transmission electron microscopy (HRTEM) revealed that tantalum carbide particles much smaller than iron grains are dispersed at the grain boundaries (mostly at tripple junctions) of iron grains. Such a configuration of the carbides hardly interrupts the intergranular magnetic coupling which reduces the effective magnetocrystalline anisotropy. It was also found by both HRTEM and temperature dependence of magnetization and coercivity that there is no distinct residual amorphous phase in the nanocrystalline Fe-Ta-C films, unlike the Fe-Cu-Nb-Si-B alloys. It was proved that the substance stabilizing the nanocrystallites in the Fe-Ta-C films is not an amorphous phase but the tantalum carbide which is thermally more stable.