Magnetization Process in Small Particles of CrO2

Initial magnetization curves, remanence, coercivity, reversible susceptibility, and rotational hysteresis have been measured for CrO2 in the form of small particles. The measurements allow rough division into three types of behavior with decreasing particle size: multidomain, or bulk behavior, for ∼100-μ particles; few-domain behavior for ∼1−10-μ particles; and single-domain behavior for particles with a length/diameter ratio ∼5 and a diameter ≤0.2 μ. The smaller particles studied were acicular and showed coercivity dominated by shape anisotropy.