| Iron-based amorphous and nanocrystalline soft magnetic alloys are one of the amorphous soft magnetic alloys with the highest saturation magnetization,the low cost to preparation and satisfying need of magnetic properties for application.In this paper,Fe-Si-B-P-C alloy targets were prepared by industrial raw materials and amorphous alloy films were fabricated by magnetron sputtering.The thickness effects of microstructure and soft magnetic properties of Fe-Si-B-P-C films were studied in detail.Thin films were vacuum annealed at different temperatures to study the effects of annealing on the microstructure and magnetic properties.In addition,the magnetic domain structure of thin films was observed by magneto-optical Kerr microscope and the motion under an applied magnetic field was monitored to understand the relationship between the magnetic anisotropy of the film sample and the internal stress and soft magnetic properties.We got the following results:1)Industrial materials were used to fabricate the Fe-Si-B-P-C alloy target for magnetron sputtering,the evolutions of microstructure and soft magnetic properties of amorphous Fe-Si-B-P-C thin films with thickness has been systematically investigated.It is revealed that all thin films with thickness ranging from 61 nm to 1210 nm exhibit a columnar structure,and the surface roughening of thin films is in accordance with the anomalous scaling,since the local roughness at typical length scales of below 100 nm rises with thickness.The coercivity,Hc,gradually decreases from 4.8 Oe for 61 nm-thick film to 0.6 Oe for 608 nm-thick film,and almost remains constant with further increasing thickness,while the magneto impedance ratio,(?Z/Z)max,rises with thickness.2)After 473 K-annealing treatment Hc decreases and(?Z/Z)max increases,which can be attributed to both the release of residual stress and the enhanced exchange coupling between higher ordered structural clusters and amorphous matrix.After annealing at 573 K,although no obvious improvement in Hc occurs,(AZ/Z)max further rises possibly due to the enhanced electrical conductivity from higher fraction of crystallization and the reduced magnetic anisotropy.However,severe crystallization takes place in all studied films when annealed at 673 K,deteriorating soft magnetic properties of thin films.Therefore,573 K-annealed Fe-Si-B-P-C thin films with 1210 nm in thickness exhibits the best soft magnetic properties with Hc of 0.3 Oe,(?Z/Z)max of 66.2%and relatively low magnetic anisotropy,which is very promising soft magnetic material for sensor application.3)The magnetic domain structure of Fe-Si-B-P-C amorphous alloy thin film is mainly characterized by stripe domains,and film thickness also affects the magnetic domain structure.When the film thickness is less than 256 nm,the existence of the striped domains cannot be observed.At this time,the demagnetizing field on the surface of thin films is larger than the perpendicular anisotropy of the film sample.When the film thickness is increased to 256 nm and above,a stripe domain with a clear boundary and a regular shape appears with a decreasing demagnetizing field.The low temperature annealing causes the residual stress to be eliminated and magnetic anisotropy of thin film surface is reduced.However,the excessive annealing temperature makes the Fe-Si-B-P-C amorphous alloy film excessively crystallized,the soft magnetic properties are destroyed,and the typical striped domains disappear. |
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