Measurement of the switching properties of a regular 2-D array of Preisach-type particles

A two dimensional array of 42 μm square pixels has been etched from a highly uniaxial 3 μm thick magnetooptical garnet film. Each pixel has a rectangular hysteresis loop, characterized by “up” and “down” switching fields H⁺ and H^-, coercivity and interaction fields, H_c and H_i. The distribution of H_c and H_i has been obtained by measuring hysteresis loops of individual pixels using an optical magnetometer. The distributions are found to be Gaussian, with the mean value coercivity H_c=258 Oe and a standard deviation of coercivity of σ_c=85 Oe. The mean interaction field H_i=0 Oe with a standard deviation of σ_i=9 Oe. The effect of the state of the magnetization of the surrounding “particles” on a given pixel is characterized by dH_i/dn=26 Oe, where n is the number of first neighbors being already switched. The number of up and down magnetized pixels versus magnetic field was counted in a polarizing microscope equipped with a magnetizing coil and thus, the magnetization and the Preisach function can be determined directly, making the identification problem straightforward for this simple Preisach system