MEASUREMENT OF THE SWITCHING PROPERTIES OF A REGULAR 2-D ARRAY OF PREISACH-TYPE PARTICLES

A two dimensional array of 42 mum square pixels has been etched from a highly uniaxial 3 mum 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 sigma(c) = 85 Oe. The mean interaction field H(i) = 0 Oe with a standard deviation of sigma(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.