Speaker
Description
Metal amorphous nanocomposites (MANC) possess properties distinct from crystalline materials due to their characteristic microstructure, which gives them excellent soft magnetic behavior. Recent research has focused on developing novel MANC compositions with superior magnetic and mechanical properties for next-generation lightweight inductor cores in electrified vehicles and rovers. In this study, we explored an alternative MANC composition of the commercially known alloy of FINEMET (Fe-Nb-Cu-Si-B), which achieves its excellent soft magnetic properties through Fe$_3$Si nanocrystals in the amorphous composite. Our alternative composition is Fe-Nb-Cu-Ga-B, where Ga has completely substituted for Si and will now form Fe-Ga nanocrystals. Fe-Nb-Cu-Ga-B ribbons were synthesized using melt-spin quenching which utilizes rapid cooling (~106°C/s) to form ribbons ~4mm wide by ~20μm thick and ~3m long. Their structural properties were characterized using x-ray diffraction (XRD) and small area electron diffraction (SAED), while magnetic properties were evaluated using vibrating sample magnetometry (VSM). VSM measurements show that Fe-Nb-Cu-Ga-B ribbons exhibit a significantly higher saturation magnetization—approximately 35% greater than traditional Fe-Nb-Cu-Si-B FINEMET alloys. Structural characterization from XRD and SAED found the presence of an ordered Fe$_3$Ga phase and a disordered Fe$_4$Ga phase. First-principles calculations were then performed to investigate the mechanism for the increased magnetization and found that the magnetic moment increased by 35% from Fe$_4$Ga to Fe$_3$Ga, correlating with the experimentally measured increase in magnetization. Based on the electronic density of states of the Fe-d orbitals, we determined that the Fe$_4$Ga phase has greater spin polarization than the Fe$_3$Ga phase. Combining theory and experiment, this integrated study provides insights into the potential of Fe-Nb-Cu-Ga-B alloys for future applications and advances the understanding of disordered nanocrystalline phases in metal amorphous nanocomposites.
