Chang Che-Hao, Su Shih-Chieh, Chang Tsun-Hsu, Chang Ching-Ray
Interdisciplinary Program of Sciences, National Tsing Hua University, Hsinchu, Taiwan.
Department of Physics, National Tsing Hua University, Hsinchu, Taiwan.
Sci Rep. 2021 Feb 8;11(1):3288. doi: 10.1038/s41598-021-82590-w.
The epoxy/magnetite nanocomposites express superparamagnetism under a static or low-frequency electromagnetic field. At the microwave frequency, said the X-band, the nanocomposites reveal an unexpected diamagnetism. To explain the intriguing phenomenon, we revisit the Debye relaxation law with the memory effect. The magnetization vector of the magnetite is unable to synchronize with the rapidly changing magnetic field, and it contributes to diamagnetism, a negative magnetic susceptibility for nanoparticles. The model just developed and the fitting result can not only be used to explain the experimental data in the X-band but also can be used to estimate the transition frequency between paramagnetism and diamagnetism.
环氧/磁铁矿纳米复合材料在静态或低频电磁场下表现出超顺磁性。在微波频率下，即在X波段，纳米复合材料呈现出意想不到的抗磁性。为了解释这一有趣现象，我们结合记忆效应重新审视了德拜弛豫定律。磁铁矿的磁化矢量无法与快速变化的磁场同步，从而导致了抗磁性，即纳米颗粒的负磁化率。刚刚建立的模型和拟合结果不仅可以用来解释X波段的实验数据，还可以用来估计顺磁性和抗磁性之间的转变频率。
