Hysteresis Branch Crossing and the Stoner-Wohlfarth Model

Scott A. Mathews

US Naval Research Laboratory
Materials & Sciences Branch
Physics Department, The Catholic University of America

Wed, April 1, 2020 - 4:00 PM
Karl Herzfeld Auditorium of Hannan Hall - Rm 108

nrl-image_photo.jpgThe Stoner-Wohlfarth model, published in 1948, predicts the crossing of magnetic hysteresis branches in single domain magnetic particles with uniaxial anisotropy. It has been widely assumed that magnetic hysteresis branches cannot or do not cross. In fact, a number of publications have referred to the crossing of hysteresis branches as being “energetically incorrect”, “non-physical”, and a “problem” with the Stoner-Wohlfarth model. This presentation reports the observation of magnetic hysteresis branch crossings in nickel films deposited on lithium niobate substrates. The hysteresis branch crossing, wherein the ascending branch of the magnetization curve crosses over the descending branch (and the descending branch crosses over the ascending branch), is demonstrated experimentally and simulated using a modified Stoner-Wohlfarth model, which takes into account thermal fluctuations and a finite distribution of magnetic anisotropy. The crossing of magnetic hysteresis branches is shown to be a robust, reproducible phenomenon.

Refreshments served at 3:45 PM

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