Toward On-and-Off Magnetism: Reversible Electrochemistry to Control Magnetic Phase Transitions in Spinel Ferrites

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• 作者：Subho Dasgupta ; Bijoy Das ; Qiang Li ; Di Wang ; Tessy T. Baby ; Sylvio Indris ; Michael Knapp ; Helmut Ehrenberg ; Karin Fink ; Robert Kruk and Horst Hahn
• 刊名：Advanced Functional Materials
• 出版年：2016
• 出版时间：November 2, 2016
• 年：2016
• 卷：26
• 期：41
• 页码：7507-7515
• 全文大小：1281K
• ISSN：1616-3028

文摘

The magnetoelectric effect, i.e., electric-field control of magnetism in artificial heterostructures is usually limited to surface/interface atoms of the magnetic materials. In order to attain electrical control of magnetism in bulk ferromagnets, this study proposes to extend the definition of magnetoelectric phenomena to include reversible, chemistry-controlled magnetization switching. A large and reversible change in the room temperature magnetization in strong ferromagnets is reported, with electrochemistry-driven Li-ion exchange; carefully chosen spinel ferrites demonstrate a reversible magnetization variation up to 50% for CuFe₂O₄ and 70% for ZnFe₂O₄. In case of CuFe₂O₄, the magnetization variation is predominantly associated with the preferential reduction of Cu²⁺ to Cu⁺ ions, and, hence, abides a nearly one-to-one relationship with the amount of injected Li-ions. In addition, the reduction of Cu²⁺ also annihilates the Fe³⁺OCu²⁺ magnetic interaction, resulting in a marked decrease in the Neél temperature of CuFe₂O₄. In contrast, the electrical tuning of superexchange interactions is found to play the decisive role in ZnFe₂O₄, where the simple electrochemical reduction model of magnetic cations can only explain a nominal fraction of the total magnetization variation, and indeed an electrochemically controlled reversible change in transition temperature is found necessary to account for the large magnetization variation observed.