Giant Room Temperature Magnetoimpedance in Doped Manganites

In the domain of magneto transport properties of materials, giant magnetoimpedance (GMI), is of research interest as it represents a large change of both real and imaginary parts of the impedance under a static magnetic field applied. Understanding of GMI needs the understanding of the micro magnetic characteristics of the materials and its dependence on dynamic magnetism. After early observation of GMI in soft magnetic amorphous wires and ribbons, the reseach has been extended to systems like polycrystals, amorphous alloys, nanocrystalline materials, single crystals and also in different structures like thin films, sandwiched structures, glass-covered microwires etc. giving a large number of papers as well as patents in the last decades. Different system display magnetoimpedance which is effective in different applications; in some, it has already been proposed and tested in laboratory prototypes, and is already on the market. Here, we will discuss the room temperature GMI property of typical polycrystalline manganites. The material preparation, characterization and magnetoimpedance properties are described in detail. The unique scaling behavior of field dependence of magnetoimpedance observed is well described by a phenomenological model.