What does a first-order reversal curve diagram really mean? A study case: Array of ferromagnetic nanowires

Abstract

The magnetic characterization technique of hysteretic materials based on the measurement of the first-order reversal curves (FORC) is one of the most appealing methods recently introduced in hundreds of new laboratories, but due to the complexity of the FORC data analysis, it is not always properly used. This method originated in identification procedures for the classical Preisach model and consequently often the FORC distribution is interpreted as a slightly distorted Preisach distribution. In this paper, we discuss this idea from two points of view derived from the basic assumptions used in the Preisach model. One is that the interaction field is equivalent with a shift of the rectangular hysteron along the applied field axis without changing the intrinsic coercivity. The other is the direct use of switching fields as coordinates, in fact, the ones defining the Preisach plane. We discuss the compatibility between the experimental FORC distribution and the Preisach model developed on the interaction field hypothesis. As a "toy model," we are using a system of ferromagnetic nanowires, explaining from the physical point of view the complex FORC diagrams as they are obtained in experiments. This explanation gives a fundament for the correct interpretation of the FORC diagram in order to get "Preisach type" information about the system, mainly about the distributions of coercive and interaction fields within the sample. These results are relevant for many ferromagnetic systems and give a valuable guide for understanding the FORC technique and its fundamental link with the Preisach model. V

Application of magneto-optical Kerr effect to first-order reversal curve measurements

“…Second, we show the separation of coercivity and bias field in an exchange bias sample, 22,23 consisting of an antiferromagnetic (AFM) and a ferromagnetic layer (FM), grown in a magnetic field high enough to saturate the FM and therefore showing a shift of the ferromagnetic hysteresis loop show a shift of the FORC distribution along the H u -axis. 16,17 Finally, we demonstrate the flexibility of the MOKE based technique and the necessity for high resolution in material science with the measurement of a gadolinium/iron sample with perpendicular magnetic anisotropy.…”

“…The shift of the H u = 0-axis can also be attributed to the canting of the magnetic moments as there is an altered interaction between the canted magnetic moments and the external field, shifting the effective field experienced by the local moments. 16,17 …”

“…While we focus here on the acquisition of high resolution FORC diagrams, further details regarding their evaluation can be found elsewhere. 16,17 B. MOKE MOKE measurements are a wide spread and easy to use technique for surface sensitive magnetization measurement. The measurement of the magnetization relies on the rotation of the polarization plane of light as it is reflected at the sample surface.…”

Temperature-dependent first-order reversal curve measurements on unusually hard magnetic low-temperature phase of MnBi

“…Later, Pike, Roberts, and collaborators conducted the first experimental procedure on geological samples [16]. Additional studies using FORC were based on nanostructured array systems [17,18,[31][32][33][34], nanocrystalline [35,36], and hard magnetic materials [19]. The FORC measurement starts in magnetic saturation.…”

“…According to the micromagnetic analysis performed by Kronmüller et al, the prevailing hardening mechanism in LTP-MnBi is due to nucleation of reversed domains [15]. A recently developed experimental method that involves the measurement of first-order reversal curves (FORCs) has been proven to be effective to study irreversible processes involved in the magnetization reversal [16][17][18][19]. It involves a measurement of a series of minor hysteresis loops starting from different reversal field points up to saturation [20].…”