Materials optimization for magnetic MEMS

By highlighting magnetomechanical effects such as the DeltaE-effect, and developing modeling code that integrates magnetoelasticity with microelectromechanical systems, it is shown that a simple cantilever system can have a sensitivity to mass loading at the attogram level. The requirements on the magnetoelastic materials for such devices are described, and progress towards achieving optimized material is reviewed. The possibility for deployment of such systems in security, healthcare, and bioscience is outline

Detailed study of the hysteresis loops for annealed amorphous alloy wires having vanishing magnetostriction

The evolution of Barkhausen events during the magnetization process in current and furnace annealed Co-based amorphous wire having vanishing magnetostriction, /spl lambda//sub s/, is reported. Their origin is explained using the core-shell model commonly accepted for this class of wire. It is argued that the application of stresses during the annealing process, in wire having slightly negative and slightly positive /spl lambda//sub s/, changes the internal magnetic domain structure. Anisotropy induced by anelastic creep can be used to avoid the formation of these Barkhausen events. The behavior of the coercivity and susceptibility is also reported

Finite-element analysis on cantilever beams coated with magnetostrictive material

The main focus of this paper is to highlight some of the key criteria in successful utilization of magnetostrictive materials within a cantilever based microelectromechanical system (MEMS). The behavior of coated cantilever beams is complex and many authors have offered solutions using analytical techniques. In this study, the FEMLAB finite-element multiphysics package was used to incorporate the full magnetostrictive strain tensor and couple it with partial differential equations from structural mechanics to solve simple cantilever systems. A wide range of geometries and material properties were solved to study the effects on cantilever deflection and the system resonance frequencies. The latter were found by the use of an eigen-frequency solver. The models have been tailored for comparison with other such data within the field and results also go beyond previous work

Transverse field-induced nucleation pad switching modes during domain wall injection

We have used magnetic transmission soft X-ray microscopy (M-TXM) to image in-field magnetization configurations of patterned Ni80F20 domain wall "nucleation pads" with attached planar nanowires. Comparison with micromagnetic simulations suggests that the evolution of magnetic domains in rectangular injection pads depends on the relative orientation of closure domains in the remanent state. The magnetization reversal pathway is altered by the inclusion of transverse magnetic fields. These different modes explain previous results of domain wall injection into nanowires

Direct imaging of domain-wall interactions in Ni80Fe20 planar nanowires

We have investigated magnetostatic interactions between domain walls in Ni80Fe20 planar nanowires using magnetic soft x-ray microscopy and micromagnetic simulations. In addition to significant monopole-like attraction and repulsion effects we observe that there is coupling of the magnetization configurations of the walls. This is explained in terms of an interaction energy that depends not only on the distance between the walls, but also upon their internal magnetization structure

DOMAIN WALL PINNING IN INHOMOGENEOUSLY DEFORMED AMORPHOUS ALLOYS

Inhomogeneous deformation in amorphous alloys is characterized by local regions of intense shear. Experiments on VITROVAC 0040 (Fe40Ni40B20) supplied by Vacuumschmelze (Hanau, Germany) show a direct correlation between the number density of the shear bands and the coercive field after inhomogeneous deformation by cold rolling. The deformation process is also shown to induce an off axis magnetic anisotropy whose mean value is large compared to other residual and induced anisotropies in these materials. On this basis a domain structure is proposed for deformed material, and a model for coercivity based on domain wall pinning at residual stresses remaining after deformation is shown to lead to reasonable estimates of the coercive force