AC-Magnetic Response Of New Type Molten Metal Thin Ribbons

With the rapid development of the mordern communication technology,the electronic technology have got a large improvement.The magnetic sensors and recording instruments are required with small size,high sensitivity and quick response.In 1992,K.Mohri et al firstly found the Giant Magneto-Impedence effect.When an AC current flows through the Co-based soft magnetic amorphous CoFeSiB wire,the AC voltage between the two ends of the wire would change sensitively with an applied magnetc field along the wire.At low frequencies,where the skin effect is very weak,this change is determined mainly by the change of inductance and it is named giant magneto inductance.But at high frequencies,the skin effect becomes very important,the field influences on both resistance and inductance are very large,so this effect is named giant magneto-impedance effect(GMI effect).At first,the most researchs on GMI were concentrated on the Co-based soft magnatic amorphous wire with vanishing or negative magnetostriction,and soon the research extended to thin ribbons,films and Fe-based soft magnetic materials. Recently,the GMI effect in soft magnetic materials has become one of the most important topics in magnetic electronics because of its important applications in various magnetic sensors and heads.This kind of magnetic sensors have many advantage,such as quick response,non-hysteresis and high sensitivity and so on.Now,the GMI effects of FeZrB and FeZrBCu thin ribbons have been researched,but FeNbB,FeNbBCu and FeNbSiB thin ribbons were not researched,and the relationship between GMI effect and the relative change of transverse permeability were seldom researched.So in order to get the new materials with high GMI effect and research the dependence of physical factors, we have done the following works.1.We prepared the Fe₈₄Nb₇B₉ and Fe₈₃Nb₇B₉Cu₁ amorphous thin ribbons by a rapid quenching technique.Then the ribbons were annealed in vacuum at 520℃-820℃andα-Fe nanograins with a size of about 9nm-14nm appeared.We measured the resistance and inductance in different outer magneticfield and current frequency, then calculated their impedance.We achieved the spectrum of GMI and the dependence of GMI via outer magnetic field and researched the relationship between GMI effect and outer magnetic field, frequency and annealing temperature.2.We measured the permeability induced by dc magnetic fields and researched the relationship between GMI effect and the relative change of transverse permeability.It showed that giant magnetoimpedance is contacted to the the change of transverse permeability and the skin effect.3.We found that There is an optimal anneal temperature for obtaining the largest giant magnetoimpedance.Fe₈₄Nb₇B₉ nano-crystal thin ribbon's optimal anneal temperature is 670℃and it's GMI(Z)_maxis -48.22%;what in Fe₈₃Nb₇B₉Cu₁ nano-crystal thin ribbon are 670℃and -54.8%.4.Compared Fe₈₄Nb₇B₉ and Fe₈₃Nb₇B₉Cu₁ nano-crystal thin ribbon, we can found that the doping of Cu element can improve the soft magnetic properties,below the ptimal anneal temperature and increase the GMI effect of the materials.