INFLUENCE OF MECHANICAL MILLING ON MAGNETIC-PROPERTIES OF INTERMETALLIC COMPOUNDS

The influence of mechanical milling on magnetic properties of various types of intermetallic compounds has been extensively investigated. It is established that, on the one hand the measurement of magnetic properties is a very sensitive probe to monitor the structural changes of intermetallic compounds during milling, and on the other hand milling may induce in the material unusual and interesting magnetic properties. The results are reviewed. It is generally observed that mechanical milling of an intermetallic compound results in atomic disorder. The disordered materials may remain in the same crystal structure or transform to a different structure, which can be the amorphous structure, a solid solution or a different complex crystalline structure. If the material is crystalline, it becomes always nanocrystalline. The magnetization of various intermetallic compounds after milling was measured at 4.2 K in the Amsterdam High Field Installation in fields up to 21 or 35 T. The high-field magnetization at 4.2 K and the magnetic susceptibility changes usually significantly and sometimes drastically as a consequence of atomic disorder and/or disorder-induced phase transformation. The magnetic ordering temperature was also measured in some compounds. The obtained results turn out to provide precise infer mation about the structural change of a compound in particular during the intermediate stage of milling. Upon disordering or phase transformation, the nature of the magnetic ordering of a compound can be markedly different from its ordered form. This is illustrated by the discovery of two novel binary concentrated spin glasses namely amorphous Co2Ge and atomically disordered crystalline GdAl2.