Reversible and quasireversible information in first-order reversal curve diagrams

Abstract

Two methods for extracting information from first-order reversal curves (FORCs) obtained on low coercivity samples are presented. The proportion of reversibility as a function of applied field can be extracted by calculating the ratio of the initial slope of each FORC to the susceptibility on the major hysteresis loop upper branch at the same field. This gives us the part of the reversal process, a process occurring with zero coercivity, that is, where H=Hr, during the magnetization reversal. In order to be able to see the nonperturbed trace coming from the irreversible processes with a small coercivity compared to the FORC domain, some points have to be added in the H<Hr area in a way that minimizes the discontinuities near H=Hr. This is done by using two functions characterizing the behavior of the magnetization on the H=Hr axis (“extrapolated FORCs”). These methods were used to characterize a CoFeB nanowire array with the applied field perpendicular to the nanowire axis.