Extracting the intrinsic switching field distribution in perpendicular media: a comparative analysis

We introduce a new method based on the first-order-reversal-curve (FORC) diagram to extract the intrinsic (microscopic) switching-field distribution (SFD) of perpendicular recording media (PRM). To demonstrate the viability of the method, we micromagnetically simulated FORCs for PRM with known SFD and compare the extracted SFD with the SFD obtained by means of two different methods that are based on recoil loops, too, which however rely on mean-field approximations and assumptions on the shape of the SFD. The FORC method turns out to be the most accurate algorithm over a broad range of dipolar interaction strengths, where the other methods overestimate the width of the SFD.Comment: 3 pages with 2 figures, 3 supplemental figures; submitted to J. Appl. Phys. (MMM Annual Conference Proceedings

The Work-Hamiltonian Connection and the Usefulness of the Jarzynski Equality for Free Energy Calculations

The connection between work and changes in the Hamiltonian for a system with a time-dependent Hamiltonian has recently been called into question, casting doubt on the usefulness of the Jarzynski equality for calculating free energy changes. In this paper, we discuss the relationship between two possible definitions of free energy and show how some recent disagreements regarding the applicability of the Jarzynski equality are the result of different authors using different definitions of free energy. Finally, in light of the recently raised doubts, we explicitly demonstrate that it is indeed possible to obtain physically relevant free energy profiles from molecular pulling experiments by using the Jarzynski equality and the results of Hummer and Szabo.Comment: 3 page