Magnetic Anisotropy in Mo-Permalloy Crystals Induced by Plane-Strain Compression

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Abstract
Magnetic properties of molybdenum Permalloy single crystals have been studied in terms of the Chikazumi‐Suzuki‐Iwata (CSI) theory of slip‐induced directional order. The crystals were deformed in a plane‐strain‐compression apparatus which restricts lateral spreading of the specimen. This type of deformation is similar to that of ordinary rolling. However, the operating slip systems required for analysis are more readily determined in plane‐strain compression, which permits slip line observations as well as analysis of specimen shape change. In this work, 4–79 Mo‐Permalloy crystals were compressed on the (110) plane and constrained to elongate in the [1̄12] direction. This orientation is particularly suitable for study in that slip occurs on only two systems {(111)[101̄] and (111̄)[011]} and that the orientation remains stable with deformation, hence avoiding possible complications due to lattice rotation. A simple analysis based on the CSI theory predicts for this orientation a slip‐induced uniaxial anisotropy with the easy axis lying between [1̄11] and [1̄10] directions on the (110) compression plane, depending on the type of ordering in the alloy. Magnetic torque measurements on disks cut from the deformed crystals indicate the presence of both long‐and short‐range order. The induced anisotropy energy Ku was found to increase with thickness reduction to a value of 120×103 erg/cm3 after 50.5% reduction. Similar results were obtained with crystals deformed by rolling.