Physical justification for negative remanent magnetization in homogeneous nanoparticles

Shuo Gu; Weidong He; Ming Zhang; Taisen Zhuang; Yi Jin; Hatem ElBidweihy; Yiwu Mao; James H Dickerson; Michael J Wagner; Edward Della Torre; Lawrence H Bennett

doi:10.1038/srep06267

Physical justification for negative remanent magnetization in homogeneous nanoparticles

Sci Rep. 2014 Sep 3:4:6267. doi: 10.1038/srep06267.

Authors

Shuo Gu¹, Weidong He², Ming Zhang³, Taisen Zhuang⁴, Yi Jin⁵, Hatem ElBidweihy⁵, Yiwu Mao⁶, James H Dickerson⁷, Michael J Wagner³, Edward Della Torre⁵, Lawrence H Bennett⁵

Affiliations

¹ 1] Department of Electrical and Computer Engineering, George Washington University, Washington, DC, 20052, USA [2].
² 1] School of Energy Science and Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China [2] Interdisciplinary Graduate Program in Materials Science, Vanderbilt University, Nashville, TN, 372345, USA [3] Vanderbilt Institute for Nanoscale Science and Engineering, Vanderbilt University, Nashville, TN, 37235, USA [4].
³ Department of Chemistry, George Washington University, Washington, DC, 20052, USA.
⁴ Department of Mechanical and Aerospace Engineering, George Washington University, Washington, DC, 20052, USA.
⁵ Department of Electrical and Computer Engineering, George Washington University, Washington, DC, 20052, USA.
⁶ Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, George Washington University, Mianyang 621900, China.
⁷ 1] Vanderbilt Institute for Nanoscale Science and Engineering, Vanderbilt University, Nashville, TN, 37235, USA [2] Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, 37235, USA [3] Department of Chemistry, Vanderbilt University, Nashville, TN, 37235, USA.

Abstract

The phenomenon of negative remanent magnetization (NRM) has been observed experimentally in a number of heterogeneous magnetic systems and has been considered anomalous. The existence of NRM in homogenous magnetic materials is still in debate, mainly due to the lack of compelling support from experimental data and a convincing theoretical explanation for its thermodynamic validation. Here we resolve the long-existing controversy by presenting experimental evidence and physical justification that NRM is real in a prototype homogeneous ferromagnetic nanoparticle, an europium sulfide nanoparticle. We provide novel insights into major and minor hysteresis behavior that illuminate the true nature of the observed inverted hysteresis and validate its thermodynamic permissibility and, for the first time, present counterintuitive magnetic aftereffect behavior that is consistent with the mechanism of magnetization reversal, possessing unique capability to identify NRM. The origin and conditions of NRM are explained quantitatively via a wasp-waist model, in combination of energy calculations.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.