Rotational magnetic measurements on recording media

Using an automated vibrating sample magnetometer, VSM, tape samples of Co treated γ-Fe2O3and CrO2particles were rotated in 5° increments in a magnetic field held constant during the rotation. Remanent magnetization measurements were made after each rotational increment. Results show that for fields greater than about 4 times the remanent coercivity, Hr, the slope of the remanent magnetization curve of a sample as a function of the applied field angle is proportional to the particle orientation distribution within the plane of the coating. Results also suggest that the minimum field necessary for particle switching occurs when the field is applied at an angle of about 45° with respect to the particle easy axis. This is consistant with earlier studies performed on single particles.