Effect Of TiO₂ Coating On Magnetic Properties Of Fe-based Nanocrystalline Ribbons

The most interesting aspect of giant magnetoimpedance(GMI)effect is its ultra-high magnetic field sensitivity in the low magnetic field region,which is widely used in highly sensitive sensors.When we design or use magnetic sensors,there exist unavoidably semiconductor materials around the sensing element.Hence,it is necessary to research how the semiconductor materials affect the magnetic properties of the magnetic material.Fe_73.5Cu₁Nb₃Si_13.5B₉nanocrystalline alloy(FINEMET)has received extensive attention since the 1980s due to its superior soft magnetic properties and a high saturation flux density.The GMI effect is often used to describe the properties of a material,but it is rarely used as a technical means to study the magnetic interaction,which provides new ideas for the understanding and application of the GMI effect.The study of magnetic interaction is beneficial to understand the intrinsic reasons of the macroscopic properties of materials,which is of great significance for the development of new magnetic materials and the design of the overall properties of materials.The main research contents of this paper are as follows:(1)Titanium dioxide(TiO₂)coating layer with different thickness was sputtered onto the smooth surface,rough surface and twin surface of FINEMET ribbon by RF magnetron sputtering.Two models,FINEMET/Ti O₂composite structural ribbons and Ti O₂/FINEMET/Ti O₂composite structural ribbons,were constructed.By analyzing the morphology,hysteresis loop and GMI effect of the composite ribbons,it is found that the GMI ratio of composite ribbons first increases and then decreases with the increase of Ti O₂layer thickness,which can be explained by the combined result of electromagnetic interaction and stress between Ti O₂thin film and the FINEMET ribbon.When the thickness of Ti O₂thin film is about 100 nm,the maximum GMI ratio of composite ribbons reaches the maximum value 57.3%,36.1%and 40.8%,respectively.Moreover,the characteristic frequencies of all composite ribbons decrease gradually with the increase of Ti O₂film thickness.In summary,Ti O₂thin film can tune the magnetic properties and GMI effect of the FINEMET ribbon,which may be applied in the field of magnetic sensor compatible with semiconductor electronics application.(2)Two models of FINEMET/Fe₂₀Ni₈₀composite ribbons and FINEMET/Ti O₂/Fe₂₀Ni₈₀composite ribbons were constructed by magnetron sputtering technology.In the FINEMET/Fe₂₀Ni₈₀composite ribbons,there exists both interface exchange interaction and dipole interaction between FINEMET ribbon and Fe₂₀Ni₈₀.The exchange interaction is a short-range force,so by changing the thickness of the interlayer Ti O₂film,the magnetic dipole interaction in the FINEMET/Ti O₂/Fe₂₀Ni₈₀composite ribbons can be studied by the peak field of GMI curve.When Ti O₂film thickness is from 40 nm to 150 nm,the dipole field generated by Fe₂₀Ni₈₀coating layer on FINEMET ribbon weakens from 2.2 Oe to 0.2 Oe.Hence,novel sensors can be designed by modulating the dipole interaction by the geometric factor K.