Cannas C, Musinu A, Piccaluga G, Fiorani D, Peddis D, Rasmussen H K, Mørup S
Dipartimento di Scienze Chimiche, Cittadella Universitaria di Monserrato, bivio per Sestu, 09042 Monserrato, Cagliari, Italy.
J Chem Phys. 2006 Oct 28;125(16):164714. doi: 10.1063/1.2354475.
The magnetic properties of cobalt ferrite-silica nanocomposites with different concentrations (15, 30, and 50 wt %) and sizes (7, 16, and 28 nm) of ferrite particles have been studied by static magnetization measurements and Mossbauer spectroscopy. The results indicate a superparamagnetic behavior of the nanoparticles, with weak interactions slightly increasing with the cobalt ferrite content and with the particle size. From high-field Mossbauer spectra at low temperatures, the cationic distribution and the degree of spin canting have been estimated and both parameters are only slightly dependent on the particle size. The magnetic anisotropy constant increases with decreasing particle size, but in contrast to many other systems, the cobalt ferrite nanoparticles are found to have an anisotropy constant that is smaller than the bulk value. This can be explained by the distribution of the cations. The weak dependence of spin canting degree on particle size indicates that the spin canting is not simply a surface phenomenon but also occurs in the interiors of the particles.
通过静态磁化测量和穆斯堡尔谱研究了具有不同铁氧体颗粒浓度（15%、30%和50%重量）和尺寸（7、16和28纳米）的钴铁氧体-二氧化硅纳米复合材料的磁性。结果表明纳米颗粒具有超顺磁行为，随着钴铁氧体含量和颗粒尺寸的增加，弱相互作用略有增强。从低温下的高场穆斯堡尔谱中，估计了阳离子分布和自旋倾斜度，这两个参数仅略微依赖于颗粒尺寸。磁各向异性常数随着颗粒尺寸的减小而增加，但与许多其他系统不同的是，发现钴铁氧体纳米颗粒的各向异性常数小于体相值。这可以通过阳离子的分布来解释。自旋倾斜度对颗粒尺寸的弱依赖性表明，自旋倾斜不仅仅是一种表面现象，也发生在颗粒内部。
