Hard Magnetic Properties of Co-Rich Microwires Crystallized by Current Annealing

Micromagnets in the form of microwires have become a subject of interest in various applications including magnetic field bias elements in miniature actuators, sensors, and manipulators. While the preparation of hard magnetic microwires with sufficiently high magnetization is a difficult task, it can be achieved by using specific crystallization techniques. We present a technique for the fabrication of micromagnets via controlled heat treatment of amorphous microwires using an electrical current. This crystallization technique converts a Co-rich microwire from a soft to a hard magnetic material. A large increase in coercivity (up to 580 Oe) is obtained after optimal current annealing (100 mA during 30-60 min). The crystallization consists of fine grains of mainly hcp-Co with an average size of 74 nm.