Stability And Controllability Of Co-based Amorphous Ribbon With Exchange Bias Behavior

The exchange bias （EB） exists in ferromagnetic/antiferromagnetic （FM/AFM） multilayerfilm systems, and the similar phenomenon can also be observed in the soft magneticamorphous ribbons with proper thermomagnetic annealing condition. While compared withtraditional FM/AFM systems, the soft magnetic amorphous ribbons have great differences instructure and produce mechanism. The Co-based ribbons with hysteresis loop shift properties ishighly worthy to further develop on Magnetic Amplifier, Single-Ended Transformer,Commodity identification tags and many other areas in the future. Thus, it is particularlyimportant to explore the physical mechanisms and techniques of the Co-based ribbons with theEB behavior.In this thesis, the Co₅₈Fe₅Ni₁₀Si₁₁B₁₆amorphous ribbons prepared by melt quenching, andthe ribbons are annealed at proper temperature. After the thermomagnetic annealing, we try toturn operation of the EB behavior by transverse positive and negative impact filed （HT） orreverse longitudinal impact filed （HRL）, in order to research on the stability and controllabilityof Co-based amorphous ribbon with EB behavior. The crystallization and microstructures ofthe samples are characterized via X-Ray Diffraction （XRD） and High Resolution ElectronicTransmission Microscopy （HRTEM）. The hysteresis loops are measured using a ballisticgalvanometer. The surface magnetic domains are scanned by the Scanning Probe Microscope（SPM）. The details of magnetic domains configuration has been analyzed based on themagnetic domain pattern. Anisotropy constants are tested by the Vector Vibrating SpecimenMagnetometer （VVSM）. The primary consequences can be cataloged as follows:The hysteresis loop of as quenched Co-based amorphous ribbons is symmetrical. Theribbons annealed at698K in air for4hour with800A/m longitudinal field, and get themaximum EB field. The f.c.c Co and Co2Si crystalline phases emerge in the amorphous matrix,and the degree of crystallization of the ribbons gradually increases with increasing theannealing temperature. When the annealing temperature reached698K, the degree ofcrystallization is most beneficial to emerge EB behavior.The EB behavior of the ribbons can be controlled by adjusting the HT. It indicates that EBfield is hardly changed when HTis smaller than critical field HT=80kA/m. In other words, theEB behavior is stable. When the HTis larger than the critical field, the EB behavior can be effectively controlled. The center of hysteresis loop will gradually shift from right side oforiginal point to symmetry, and the pattern of maze domain from clear-cut to indistinct. Inaspect of the anisotropy constants, uniaxial anisotropy constants （K1） increase, andunidirectional anisotropy constants （K2） decrease.The EB behavior can also be controlled by adjusting the HRL. The EB behavior is stablewhen HRLis smaller than critical field HRL=5kA/m; when the HTis larger than the critical field,the EB behavior can be effectively controlled. The center of hysteresis loop will gradually shiftfrom right side of original point to the left, and the pattern of maze domain from clear-cut toindistinct, and then become clear. In aspect of the anisotropy constants, K1increase and thendecreases, and K2decreases and then increases.