Development of an (Fe, Sn)-based Nanocrystalline Soft Magnetic Alloy

Abstract

The D03 Fe3Sn phase shows higher magnetization and smaller magnetocrystalline anisotropy compared to Fe3Si based on the comprehensive first principles calculations. For this reason, it is important to develop nanocrystalline soft alloys which have D03 Fe3Sn phase as primary crystallite. A new alloy design method, motivated by the work of Villars, was used to choose the alloy composition. Element Co was found to stabilize the D03 Fe3Sn phase. In this work, a new alloy system (Fe1-x-yCoxSny)87Nb3B9Cu1 was studied to achieve D03 Fe3Sn phase with the help of the non-equilibrium processing method. Differential scanning calorimetry was used to determine the primary crystallization temperatures of the amorphous ribbons. The amorphous ribbons were annealed in tube furnace at 723K, 773K, and 823K for 3600 seconds after encapsulating them in a fused quartz ampoule. X-Ray Diffraction (XRD) has been used to analyze structural properties of as-spun and heat-treated ribbons of all alloy compositions. The single broad peak of Fe60Co20Sn7Nb3B9Cu1 as-spun ribbons’ XRD diffractograms indicates an amorphous phase due to their lack of long-range order. The rest as-spun ribbons’ XRD diffractograms shows partial crystalline during melt-spinning process due to the low glass-forming ability of these series of alloys. XRD diffractogram of the heat-treated ribbons are comprised of a B2 phase, which has a BCC structure. The crystallite sizes for each heat-treated sample were estimated by Scherrer broadening to have values between 7 and 10 nm. The magnetic properties of as-spun and heat-treated ribbons were studied by vibrating sample magnetometry. Saturation magnetization and coercivity were determined from room temperature magnetic hysteresis loops. The highest magnetization value achieved was 161.7 Am2/kg for the Fe75Co4Sn8Nb3B9Cu1 ribbon annealed at 723K. **