Bicrystal cluster structure and magnetic properties of CoCrTa/Cr thin film media

Abstract

Structures of bicrystal clusters of CoCrTa thin film media are examined using high resolution transmission electron microscopy (HRTEM), and the effects of the bicrystal clusters on magnetic hysteresis were studied using micromagnetic simulation. The bicrystal cluster of CoCrTa consists of two crystallographic variants grown on a single Cr underlayer grain with their c-axes normally-aligned in the film plane. The typical number of grains in each cluster is 2 to 3. With the bicrystal structure, coercivity decreases significantly as grain size decreases when intergranular exchange coupling is strong, and high hysteresis squareness can be obtained. Coercivity in the small grain size region can be increased by reducing the exchange coupling.