Key Laboratory for Magnetism and Magnetic Materials of MOE, Lanzhou University, Lanzhou 730000, People's Republic of China.
Nanoscale Res Lett. 2013 Oct 1;8(1):404. doi: 10.1186/1556-276X-8-404.
We report an adjustable magnetic resonance frequency from 1.45 to 2.54 GHz for NiFe2O4 nanoparticles which were prepared by a sol-gel process. X-ray diffraction and scanning electron microscopy results indicate that the samples are polycrystalline nanoparticles, and the size of the particles increases obviously with the thermal treatment temperature. The consequence of the surface composition suggests that the oxygen defects are present in the nanoparticle surface, and this surface magnetic state can show a strong surface anisotropy. With decreasing size of the particle, the surface magnetic effect is predominant, resulting in an increase of resonance frequency for NiFe2O4 nanoparticles. This finding provides a new route for NiFe2O4 materials that can be used in the gigahertz range.
我们报告了一种可调磁共振频率，范围从 1.45 到 2.54GHz，针对的是通过溶胶-凝胶工艺制备的 NiFe2O4 纳米粒子。X 射线衍射和扫描电子显微镜结果表明，这些样品是多晶纳米粒子，并且随着热处理温度的升高，粒子的尺寸明显增大。表面成分的结果表明，纳米粒子表面存在氧缺陷，这种表面磁状态可以表现出强烈的表面各向异性。随着粒子尺寸的减小，表面磁效应占主导地位，导致 NiFe2O4 纳米粒子的共振频率增加。这一发现为可以用于千兆赫兹范围的 NiFe2O4 材料提供了一条新途径。
