Oberdick S D, Borchers J A, Krycka K L
Department of Physics, University of Colorado, Boulder, Colorado 80309, USA.
National Institute of Standards and Technology, Boulder, Colorado 80305, USA.
Appl Phys Lett. 2022;120(5). doi: 10.1063/5.0081922.
We have investigated the magnetic correlations among 7 nm iron oxide nanoparticles embedded in stretched silicone elastomers using polarized Small Angle Neutron Scattering (SANS). The magnetic nanoparticle (MNP)-elastomer composite can be stretched during experiments, and macroscopic deformations cause rearrangement of the iron oxide particles on the nanoscale. Polarized neutrons can be used to nondestructively probe the arrangement of magnetic nanoparticles before and after stretching, so that the relationship between applied stress and nanoscale magnetization can be interrogated. We find that stretching the MNP-elastomer composite past a certain threshold dramatically changes the structural and magnetic morphology of the system. The unstretched sample is modeled well by ~40 nm clusters of ~7 nm particles arranged in a hard sphere packing with a "volume fraction" parameter of 0.3. After the sample is stretched 3× its original size, however, the scattering data can be modeled by smaller, 16 nm clusters with a higher volume fraction of 0.4. We suggest that the effect can be understood by considering a stretching transformation on FCC-like crystallites of iron oxide nanoparticles embedded in an elastomeric medium.
我们使用极化小角中子散射（SANS）研究了嵌入拉伸硅橡胶弹性体中的7纳米氧化铁纳米颗粒之间的磁相关性。磁性纳米颗粒（MNP）-弹性体复合材料在实验过程中可以被拉伸，宏观变形会导致纳米尺度上氧化铁颗粒的重新排列。极化中子可用于无损探测拉伸前后磁性纳米颗粒的排列，从而探究施加应力与纳米尺度磁化之间的关系。我们发现，将MNP-弹性体复合材料拉伸超过某个阈值会显著改变系统的结构和磁形态。未拉伸的样品可以用约40纳米的团簇来很好地建模，这些团簇由约7纳米的颗粒组成，排列成硬球堆积，“体积分数”参数为0.3。然而，在样品被拉伸至其原始尺寸的3倍后，散射数据可以用更小的、16纳米的团簇来建模，其体积分数更高，为0.4。我们认为，可以通过考虑对嵌入弹性体介质中的氧化铁纳米颗粒的类面心立方微晶进行拉伸转变来理解这种效应。
