Tracking the individual magnetic wires' switchings in ferromagnetic nanowire arrays using the first-order reversal curves (FORC) diagram method

The complex hysteretic properties observed in structured ferromagnetic materials can be revealed with remarkable details in magnetization processes like the first-order reversal curves (FORC) - a characterization technique extensively used in recent years. The really fundamental problem in the analysis of experimental FORC diagrams is related to the possibility to link the hysteretic properties of real physical entities in a unique way with regions from the FORC distributions. Actually, what many scientists are often doing is to use a Preisach-type interpretation of FORC data without a proof for the accuracy of this procedure. In this paper we analyze in detail the relation between the switching events of physical entities given by the Preisach function and the FORC distribution in magnetic nanowire arrays with the aim to show the limits of the conventional interpretation of FORC data. For this type of sample we show how the real switching events are contributing to the experimental diagram. We present in a systematic manner the way in which the switchings of the physical wires are observed multiple times (both as positive or negative contributions). The multiplicity of switching occurrences is not the same for all the wires in the sample, being dependent on the wire intrinsic coercivity and its position in the array. In this manner one can track the switchings contributions of real magnetic wires on the FORC diagram.