Anisotropy in the Magnetic Composite Drawn Wire for Memory Applications

Abstract

The magnetic composite wire for memory applications made by the cladding and drawing method has been developed. The origin of magnetic anisotropy in the composite wire was investigated. Magnetic composite wires 0.1 mm in diameter which consisted of CZC (0.80%Cr-0.20%Zr-bal Cu) as the core and Mo-permalloy (81.3%Ni-4.5%Mo-0.4%Mn-bal Fe) as the surface layer 3,4 and 8 μm in thickness were made, and hysteresis loops in the axial and circumferential directions as well as output voltages as the memory element were measured.
In the cold-drawn composite wires there exists strong anisotropy with the easy direction in the wire axis. In the composite wires annealed near 600°C, however, anisotropy with the easy axis in the circumferential direction grows. This anisotropy desirable for memory applications becomes remarkable as the thickness of the magnetic layer decreases. In expectation of strain-induced anisotropy, lattice spacing in the magnetic layer, dilatation of CZC and Mo-permalloy, tensile strength of the composite wires, etc. were measured. In the composite wire with the easy axis in the circumferential direction, the residual stress in the magnetic layer is anisotropic; compressive in the circumferential and tensile in the axial and radial directions.
As the result, it was concluded that the combination of anisotropic residual stress and negative magnetostriction in the magnetic layer favors the magnetization in the circumferential direction.