Sasaki Stephen S, Udalov Oleg G, Kurish Jeffrey A, Ishii Momoko, Beloborodov Igor S, Tolbert Sarah H
Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095, United States.
Department of Physics and Astronomy, California State University Northridge, Northridge, California 91330, United States.
ACS Appl Mater Interfaces. 2022 Apr 13;14(14):16505-16514. doi: 10.1021/acsami.1c20599. Epub 2022 Mar 30.
In this work, we demonstrate an experimental realization of a granular multiferroic composite, where the magnetic state of a nanocrystal array is modified by tuning the interparticle exchange coupling using an applied electric field. Previous theoretical models of a granular multiferroic composite predicted a unique magnetoelectric coupling mechanism, in which the magnetic spins of the ensemble are governed by interparticle exchange. The extent of these exchange interactions can be controlled by varying the local dielectric environment between grains. We specifically utilize the strong dielectric dependence of ferroelectric materials to modify the interparticle coupling of closely spaced magnetic nanoparticles using either a change in temperature or an electric field. This coupling modifies the ensemble magnetic coercivity and thus the superparamagnetic-to-ferromagnetic phase transition temperature. Through the use of two different ferroelectrics, our results suggest that this magnetoelectric coupling mechanism could be generalized as a new class of multiferroic material, applicable to a broad range of ferroelectric/magnetic nanocrystal composites.
在这项工作中，我们展示了一种颗粒状多铁性复合材料的实验实现，其中通过施加电场调节颗粒间交换耦合来改变纳米晶体阵列的磁状态。先前颗粒状多铁性复合材料的理论模型预测了一种独特的磁电耦合机制，其中整体的磁自旋由颗粒间交换作用支配。这些交换相互作用的程度可以通过改变颗粒间的局部介电环境来控制。我们具体利用铁电材料对介电的强烈依赖性，通过改变温度或施加电场来改变紧密排列的磁性纳米颗粒之间的颗粒间耦合。这种耦合改变了整体的磁矫顽力，进而改变了超顺磁到铁磁的相变温度。通过使用两种不同的铁电体，我们的结果表明，这种磁电耦合机制可以推广为一类新型的多铁性材料，适用于广泛的铁电体/磁性纳米晶体复合材料。
