TODAY: Anjanroop Singh, 30-Jan-24, 12:20pm Central
1 view
Skip to first unread message
Ellad Tadmor
Jan 30, 2024, 7:52:06 AMJan 30
to aem-solid...@umn.edu
AEM Mechanics Research Seminar
Tuesday 30-Jan-2024, 12:20pm Central
Mr. Anjanroop Singh
Department of Aerospace Engineering and Mechanics, University of Minnesota
Title: Design of materials with small magnetic hysteresis: the unexpected role of magnetostriction
Abstract: Numerous studies in the 1950s-1970s based on linear stability analysis of the single domain state on the shoulder of the hysteresis loop show that this method fails to predict the width of the loop, a conclusion referred to as the ``coercivity paradox’'. We argue that the basic idea of using micromagnetics to predict coercivity is reasonable, but the fault lies with linear stability analysis; one needs to account for large but localized disturbances arising from potent defects. To investigate the prediction of coercivity in this context, we develop an implementation of micromagnetics using the magnetization and vector potential as basic unknowns using the recent work of Di Fratta et al. (SIAM J. Math. Anal. 52, (2020), 10.1137/19M12613652020), and we borrow ideas from the strategy of Balakrishna et al. (npj Computational Materials 8, (2022), 10.1038/s41524-021-00682-7). We have developed a strategy with minimal assumptions, for a soft magnetic material like FeNi, to predict the coercivity and the evolution of magnetic domain patterns under the varying applied field at nano and macro scales. The value of coercivity is controlled by various material parameters like anisotropy constant or exchange constant and so forth. Introducing at the nanoscale largely localized disturbances through defects, a nucleation barrier for the reversal of the magnetization is provided. We have demonstrated that the change in the size of localized disturbance affects the coercivity because the exchange is dominant at the nanoscale. We have also shown that the introduction of magnetostriction(magneto-elastic energy) affects the nucleation barrier, which forces the magnetization to take an alternative path consistent with strain compatibility that in turn increases the coercivity of the material. These alternative paths are seen with completely different magnetic domain patterns formed as local minimizers with the changing applied field. We find that small values of magnetostriction have an important effect on coercivity. The predictions are in a form that can be used for alloy development of soft magnetic materials.
For more information, visit the AEM Mechanics Research Seminar website:
Tuesday 30-Jan-2024, 12:20pm Central
In-person: Room 402, Walter Library, University of Minnesota
Online: Webinar registration link
Department of Aerospace Engineering and Mechanics, University of Minnesota
Title: Design of materials with small magnetic hysteresis: the unexpected role of magnetostriction
Abstract: Numerous studies in the 1950s-1970s based on linear stability analysis of the single domain state on the shoulder of the hysteresis loop show that this method fails to predict the width of the loop, a conclusion referred to as the ``coercivity paradox’'. We argue that the basic idea of using micromagnetics to predict coercivity is reasonable, but the fault lies with linear stability analysis; one needs to account for large but localized disturbances arising from potent defects. To investigate the prediction of coercivity in this context, we develop an implementation of micromagnetics using the magnetization and vector potential as basic unknowns using the recent work of Di Fratta et al. (SIAM J. Math. Anal. 52, (2020), 10.1137/19M12613652020), and we borrow ideas from the strategy of Balakrishna et al. (npj Computational Materials 8, (2022), 10.1038/s41524-021-00682-7). We have developed a strategy with minimal assumptions, for a soft magnetic material like FeNi, to predict the coercivity and the evolution of magnetic domain patterns under the varying applied field at nano and macro scales. The value of coercivity is controlled by various material parameters like anisotropy constant or exchange constant and so forth. Introducing at the nanoscale largely localized disturbances through defects, a nucleation barrier for the reversal of the magnetization is provided. We have demonstrated that the change in the size of localized disturbance affects the coercivity because the exchange is dominant at the nanoscale. We have also shown that the introduction of magnetostriction(magneto-elastic energy) affects the nucleation barrier, which forces the magnetization to take an alternative path consistent with strain compatibility that in turn increases the coercivity of the material. These alternative paths are seen with completely different magnetic domain patterns formed as local minimizers with the changing applied field. We find that small values of magnetostriction have an important effect on coercivity. The predictions are in a form that can be used for alloy development of soft magnetic materials.
For more information, visit the AEM Mechanics Research Seminar website:
---
Ellad B. Tadmor, Ph.D.
Russell J. Penrose Professor
Department of Aerospace Engineering and Mechanics
University of Minnesota
https://dept.aem.umn.edu/~tadmor/
Russell J. Penrose Professor
Department of Aerospace Engineering and Mechanics
University of Minnesota
https://dept.aem.umn.edu/~tadmor/
Reply all
Reply to author
Forward
0 new messages