The FORC α.M2.S method and its applications

First-order-reversal-curve (FORC) diagrams are eminently suitable for extracting the intrinsic (microscopic) switching-field distribution (SFD) for a wide variety of magnetic systems, including soft and hard magnets, perpendicular recording media (PRM) and permanent magnets. First, we represent the interactions as a mean field alpha and a fluctuating component. Next, the statistical properties of the FORC diagrams are analyzed. We systematically investigate which moment M of the SFD is most appropriate to isolate the mean field alpha and the SFD. We found that the second moment M2 provides both the most robust platform as well as the most accurate procedure, defining the "FORC. alpha.M2.Srdquo method. The method is completed by an extrapolation scheme to recover data-details, masked by a smoothing step S, which is necessary to take numerical derivatives. The FORC alpha.M2.S method is demonstrated by a micromagnetic simulation of a typical PRM model with a SFD of known width and shape, then extracting the SFD of the model by the FORC. alpha.M2.S method and finally comparing the extracted SFD to the known SFD. Our test shows that the width differs from the known value by less than 5% over a broad range of exchange coupling strength.