Magnetic distributions of iron-(nickel zinc ferrite) nanocomposites from first order reversal curve analysis
Magnetic distributions of iron-(nickel zinc ferrite) nanocomposites from first order reversal curve analysis
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DOI：
10.1063/1.4803545
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发表时间：
2013-05-07
影响因子：
3.2
通讯作者：
Dennis, C. L.
中科院分区：
文献类型：
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作者：
Giri, Anit K.;Hirsh, Gary;Dennis, C. L.
一阶反转曲线测量为量化材料中的磁性分布提供了一种强有力的方法。在这里，我们用这种方法量化了Fe-(Ni0.5Zn0.5)Fe2O4纳米复合材料的磁性质分布，并了解了影响其磁各向异性的纳米机制。采用铁氧体沉淀和控制还原的化学方法合成了Fe-(Ni0.5Zn0.5)Fe2O4纳米复合粉末，并在铁氧体内部形成了铁纳米团簇。对两个铁含量分别接近65%和6%的样品进行了研究。透射电子显微镜测量得到的颗粒平均尺寸接近15 nm(相当于65%Fe)和60 nm(相当于6%Fe)。合成的纳米复合材料在7T时的磁化强度(M-7T=58am-2 kg(-1))接近(Ni0.5Zn0.5)Fe2O4的体磁饱和磁化强度(60am-2 kg(-1))。这在这些铁氧体系统中并不典型，因为结晶度较差。在我们的样品中，观察到的大的M-7T可能是由于铁纳米团簇的存在以及结晶度的提高。然而，在高场下的磁化强度有一个斜率，这通常被归因于表面自旋倾斜。相反，这可能是纳米颗粒表面结晶度降低的迹象，特别是在类似于65%Fe的样品中。此外，两个样品中铁素体和铁纳米团簇之间相互作用的不同导致了不同的各向异性分布，第一个样品向饱和的转变较宽，第二个样品的转变更尖锐，并通过一阶反转曲线测量证实了这一点。
First order reversal curve measurements offer a powerful approach to quantify the magnetic property distributions in materials. Here, we have used this approach to quantify magnetic property distributions and understand the nano-scale mechanisms contributing to the magnetic anisotropy of Fe-(Ni0.5Zn0.5)Fe2O4 nanocomposites. The Fe-(Ni0.5Zn0.5)Fe2O4 nanocomposite powders were synthesized using a chemical method involving ferrite precipitation and controlled reduction which resulted in the formation of iron nanoclusters within the ferrite. Two samples with a similar to 65% and similar to 6% iron composition, respectively, were studied. Transmission electron microscopy measurements yielded an average particle size of similar to 15nm (similar to 65% Fe) and similar to 60nm (similar to 6% Fe). The magnetizations at 7 T for the synthesized nanocomposites (M-7T = 58 Am-2 kg(-1) for the similar to 65% Fe sample and 55 Am-2 kg(-1) for the similar to 6% Fe sample) are close to that of the bulk saturation magnetization (similar to 60 Am-2 kg(-1)) of (Ni0.5Zn0.5)Fe2O4. This is not typical in these ferrite systems, due to poor crystallinity. In our samples, the observed large M-7T may result from the presence of the iron nanoclusters, as well as improved crystallinity. However, there is a slope to the magnetization at high fields which has typically been attributed to surface spin canting. This may instead be an indication of reduced crystallinity at the surface of the nanoparticles, especially in the similar to 65% Fe sample. Furthermore, a difference in interactions between the ferrite and the iron nanoclusters in the two samples results in different anisotropy distributions, as evidenced by a broad transition to saturation for the first sample, and a much sharper transition for the second sample, and confirmed through first order reversal curve measurements.