Comment on "The mathematical origins of the kinetic compensation effect" parts 1 and 2 by P. J. Barrie, Phys. Chem. Chem. Phys., 2012, 14, 318 and 327.

The concept of kinetic compensation and the associated isokinetic relation continue to be subject to debate, despite the fact that the conditions under which they are to be expected are now well established, and the criteria for deciding that they have been observed are known. We present these conditions and criteria, and the reality of these relations, and stress their importance for catalysis. We then discuss the fact that statistical arguments against their reality continue to be presented. Recently two articles, based upon the statistical point of view have been published in this Journal. We show that, despite the fact that the mathematics of these articles is error free, they present a distorted image of the present understanding of the subject.

Magnetostatic interactions and coercivities of ferromagnetic soft nanowires in uniform length arrays.

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.

First order reversal curves (FORC) diagrams of Co nanowire arrays.

Nanowire arrays of Co and Ni have been obtained by current pulse electrodeposition into nanoporous alumina templates. By adjusting the pH of the bath, the microstructure of the Co wires was tailored, resulting in two types of arrays of crystalline Co--hcp, with c-axis nominally parallel (Co (c parallel)), or nominally perpendicular (Co (c perpendicular)) to the wire. First-order reversal curve (FORC) diagrams provide information on average coercivity of the individual nanowire and the factors influencing the field created in the saturated array by the magnetostatic interactions. The dependences of this field on array geometry (wire length and diameter) and saturation magnetization were found to be in excellent agreement with theoretical predictions from a micromagnetic model. For arrays with lower wire diameter, the average coercivity of the individual wires is systematically higher than the coercivity of the array. The most important difference between the two Co series is in the dependence of the FORC diagrams on the wire diameter, with the Co (cl) showing significant pattern changes at large diameters. Two possible sources of those changes are discussed.

Statistical study of effective anisotropy field in ordered ferromagnetic nanowire arrays.

Soft ferromagnetic nanowire arrays were obtained by electrodeposition of Co-Fe-P alloy into the pores of high quality home-made anodized aluminum oxide (AAO) templates. Bath acidity and current density were the two parameters used in order to tailor the orientation of local anisotropy axes in individual nanowires. In order to quantify the influence of the induced anisotropies on the magnetization processes in individual nanowires, the in-plane magnetization loops of the arrays are modeled as log-normal distributions of Stoner-Wohlfarth transverse magnetization processes. Using the lognormal mean parameter as an approximation for the saturation applied field of the array, we compute the effective anisotropy of the nanowires, which is found to increase with the pH of the electrodeposition bath.