Tunable Magnetic Anisotropy In Amorphous-Fiber-Based Structures For Multiferroic Applications INVITED

Abstract

Magnetization reversal in 1D structures attracts increasing interest due to its connection with the development of novel spintronics, logic devices, actuators and manipulators for nano-sized objects. Amorphous micro-scale objects (stripes, films, rods) are attractive as materials with an extremely high magnetic softness, but difficult to be studied because of amorphous state and macro scale. Magnetic domain structure and magnetization reversal mechanism in amorphous fibers are defined by magnetoelastic energy, which leads to (i) very sensitive tunability of magnetic anisotropy and (ii) unusually fast domain wall propagation when reversing the magnetization. The role of relaxation processes under current annealing and conventional annealing in initially stressed amorphous materials is considered as a part of the complex process involving both magnetostriction constant change and stress components redistribution [1, 2]: a sign of the magnetostriction can be changed through annealing, which leads to the change of a type of magnetic domain structure. Moreover, the relationships between anisotropy constant and characteristics of domain wall dynamics are established: anisotropy value at the fiber axis enters the expressions for domain wall width, length, slope, velocity and mobility, whereas rate of anisotropy radial variation influences only on the length of domain wall [3]. Configuration of the head-to-head domain wall is visualized as a particular solution of Landau-Lifshitz-Gilbert equation. 1D amorphous fibers are considered as prospective magnetic materials suitable for multiferroic applications especially when they are incorporated into piezo-polymer matrices [4]. Due to the sensitivity of soft magnetic materials to low magnetic field, this approach can be used for the design of new self-biased magnetoelectric composites that provide large ME coupling under an external AC magnetic field in the absence of a DC magnetic field.