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(a) Schematic representation of the main loop and of a minor loop in hard magnetic materials in which magnetization reversal occurs by discrete switching. Points and are characterized by identical values of the sample magnetization and they divide the minor loop into two equal parts. The associated applied magnetic fields are and . The effective demagnetizing field, , is the same in and , equal to . (b) Schematic drawing of the coercivity distribution function . The left part represents the part, , of the distribution function, for which the grains’ moments reverse during minor loop measurements. The right part represents the part of the distribution function, , for which the grains’ moments remain unchanged during minor loop measurements.
Simulated minor hysteresis loops for a system made of exchange-decoupled dipolar-coupled magnetic cubes with perpendicular magnetization. Inset: effective demagnetizing factor, , derived from the hysteresis loops.
Experimental major and minor hysteresis loop for a thick NdFeB film with perpendicular to plane magnetization. Inset: extracted dependence of the effective demagnetizing field on magnetization .
Hard Demag factor ( where is the sample-shape demagnetizing factor and is the grain self-demagnetizing field), (effective demagnetizing factor derived from the simulated hysteresis cycles), slope of the calculated main loop, slope characterizing the assumed distribution, and slope of the calculated loop after application of the corrections. The variations from one system to another in the slope representing the intrinsic distribution and the corrected loops are due to statistical errors resulting from the small size of the considered systems.
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