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

A two dimensional array of 42 /spl mu/m square pixels has been etched from a highly uniaxial 3 /spl mu/m thick magnetooptical garnet film. Each pixel has a rectangular hysteresis loop, characterized by "up" and "down" switching fields H/sup +/ and H/sup /spl minus//, coercivity and interaction fields, H/sub c/ and H/sub i/. The distribution of H/sub c/ and H/sub 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/sub c/=258 Oe and a standard deviation of coercivity of /spl sigma//sub c/=85 Oe. The mean interaction field H/sub i/=0 Oe with a standard deviation of /spl sigma//sub i/=9 Oe. The effect of the state of the magnetization of the surrounding "particles" on a given pixel is characterized by dH/sub 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.<
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