Preparation Of Permalloy Glass-covered Microwires Using Melt Spun Method

The phenomenon that the AC impedance of magnetic materials changes significantly under the external magnetic field is called Giant Magnetoimpedance (GMI) effect. It is found that the GMI effect is closely related to the soft magnetic properties and magnetic domain structure of materials. As soft magnetic materials can be prepared by high frequency induction melting, their soft magnetic properties can be optimized by changing chemical compositions and preparation process (such as melting process and heat treatment), which provides the possibility of preparation of microwires raw materials. This thesis first introduces method of vacuum induction melting which is used to prepare permalloy, the results focus on the performance of the soft magnetic alloy with different permalloy components, melting time and the position of the samples. And then, permalloy glass-covered microwires are prepared by the Talor-Ulitovsky method, the dependence of GMI and soft magnetic properties with the length is discussed. The main contents are as follows:1.The effect of soft magnetic properties of permalloy with different components and melting process(1) Permalloy Fe19.8Ni80.2has the better soft magnetic properties.(2) At the start stage of the melting, metal powder is not completely melted. The softness of the material on the edge is better than internal central part. During refining stage, the metal powder is utterly melted, the result is the opposite.(3) Along with the increase of the smelting time, material structure tends to be more uniform, and the soft magnetic properties will be better.When Fe and Ni powder has been smelted for12min, among three kinds of permalloy (Fe19.8Ni80.2, Fe19.4Ni80.6and Fe18.7Ni81.3), maximum permeability (μmax) of internal central part of Fe19.8Ni80.2and Fe19.4Ni80.6reach5.18×104and6.18×104respectively. The initial permeability (μi) of Fe19.8Ni80.2is the3.89×104, and anisotropy field (Hk) is the2.45Oe. Yet, μmax and μ1of sputtering target material (Fe20.0Ni80.0) are only1.76×104and1.59×104respectively. Obviously, μmax and μi of Fe19.8Ni80.2are more than twice as much as the target material.2. The GMI effect and soft magnetic properties of Fe19.8Ni80.2microwares with different length(1) With the length decrease of Fe19.8Ni80.2glass-covered microwires, the GMI ratio decreases quickly. The maximum GMI ratio of the microwires with3.8cm and2cm in length reaches235%and191%, respectively. The circumferential anisotropy field (Hk) of the microwire with2cm in length is1.7Oe.(2) With the length decrease, soft magnetic properties of glass-covered microwires declines. When the wire length reduces to2cm, this effect is evident and its softness is the best.