Texturing of magnetic materials at high temperature by solidification in a magnetic field

Abstract

THE ability to impose a preferred orientation, or 'texture', on a crystalline material is important in many fields of materials science. In general, crystalline materials are more or less anisotropic in their properties, depending on their lattice structure, and texturing allows the most favourable direction (for example, for current flow or magnetic susceptibility) to be used in applications. Ferromagnetic materials can be textured by 'magnetic annealing'—the orientation of powdered material in a magnetic field, usually followed by a sintering step—but this must be done at temperatures below the material's Curie temperature. Here we present a new method of texturing materials that have a residual anisotropy in their magnetic susceptibility at high temperature, by solidification in a magnetic field. This one-step process, which may be called 'paramagnetic annealing', is demonstrated by application to the high-temperature superconductor YBa₂Cu₃O₇.