Magnetostatic Interactions and Coercivities of Ferromagnetic Soft Nanowires in Uniform Length Arrays

Abstract

First-order reversal curve diagrams have been used to investigate magnetostatic interactions and average coercivity of individual wires in soft ferromagnetic uniform length nanowire arrays. We present a method for identifying these physical parameters on the out-of-plane first-order reversal curve diagrams: the position of the irreversible part on the critical axis is a good approximation to the average value of the nanowire coercivity and the maximum interaction field is equal to the interaction field at saturation. Their dependence upon material (CoFeB and Ni) and nanowire length are presented. The magnetostatic interactions increase linearly with length, in agreement with a model developed previously. The global array coercivity, obtained from magnetization curves, is generally lower than the apparent average coercivity for individual nanowires. This coercivity reduction increases linearly with the magnetostatic interactions. The general shape of the out-of-plane first-order reversal curve diagrams is compared with those obtained from a theoretical moving Preisach model.

Magnetic interactions and reversal mechanisms in Co nanowire and nanotube arrays

“…For most NW array systems, the maximum observed in the FORC diagram can be associated to a good approximation with the average value of the NW coercivity (H FORC c ). 28 However, for small diameters (d $ 40 nm) we found a high coercivity distribution along the H c axis. In these cases the maximum value of the FORC diagram cannot be associated with H FORC c as previously reported.…”

“…The FORC method has proved to be an effective way to characterize magnetic interactions and magnetization reversal in nanomagnet arrays. [28][29][30][31]41 To obtain FORCs one first has to saturate the sample applying a large positive magnetic field. Then, we lower H to the so-called reversal field H r (not yet sufficient to saturate the sample in the negative direction), and measure the magnetization M as a function of H, varying H from H r to the positive saturation field value.…”

“…10 Various models have been recently developed for the interpretation of FORC results applied to arrays of nanowires. 11,28,30,32 These models then enable one to extract quantitative information on the coercivity distribution of individual nanowires, interaction field at saturation, and obtain insights into the magnetization reversal mechanism. For a better interpretation of the FORC measurements, it is usual to plot the FORC diagram as a contour plot of the FORC distribution (Fig.…”

“…Using the moving Preisach model, 28,33 that also takes into consideration the interactions between the mathematical hysterons, the interaction field at saturation can be approximated by 28…”

Characterization of the magnetic interactions of multiphase magnetocaloric materials using first-order reversal curve analysis

“…The lack of clear FORC distribution delimitation prevents us to extract a precise interaction field value, but a good estimate can be taken as half the distance between peaks A and B. 14,15 All composite samples present a qualitatively similar behavior, with interaction fields of 1.1 6 0.2 Oe.…”