Effect of submicrometer clustering on the magnetic properties of free-standing superparamagnetic nanocomposites
Effect of submicrometer clustering on the magnetic properties of free-standing superparamagnetic nanocomposites
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DOI：
10.1021/jp8039548
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发表时间：
2008-08-28
影响因子：
3.7
通讯作者：
Baldomir, Daniel
中科院分区：
文献类型：
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作者：
Hoppe, Cristina E.;Rivadulla, Francisco;Baldomir, Daniel
利用油酸包覆磁赤铁矿纳米粒子，获得了纳米填料在基体中分布均匀的超顺磁性聚合物纳米复合材料。均匀分散的磁性薄膜和由亚微米纳米颗粒（NP）簇分布构成的分散体都可以从同一批磁性纳米颗粒开始获得。我们证明，这些材料的磁性行为的差异仅是纳米粒子空间分布变化的线索，不涉及其尺寸或总体积分数的变化。 NP 随机分布的实验行为与在等效系统上进行的蒙特卡罗 (MC) 模拟一致。相反，由于聚集体中纳米粒子局部浓度的增加而产生偶极相互作用强度的增加，聚集体的存在产生了更高的阻断温度（T-B）值。通过这种方式，我们确定即使在亚微米范围内，聚类也能强烈控制纳米复合材料的磁性行为。这对于设计具有技术应用的新型磁性材料至关重要。
Superparamagnetic polymer nanocomposites with well differenced distribution of the nanofiller in the matrix were obtained by using oleic acid-coated maghemite nanoparticles. Both homogeneously dispersed magnetic films and dispersions constituted by a distribution of subrnicrornetric nanoparticle (NP) clusters could be obtained starting from the same batch of magnetic NPs. We demonstrated that differences in the magnetic behavior of these materials are solely clue to changes in the NP spatial distribution not involving changes in their size or total volume fraction. The experimental behavior of random distributions of NPs was consistent with Monte Carlo (MC) simulations performed on equivalent systems. On the contrary, the presence of aggregates produced higher values of the blocking temperatures (T-B) due to an increase in the strength of dipolar interactions produced by an increase of the local concentration of NPs in the aggregates. In this way, we determined that clustering, even in the submicrometric range, strongly controls the magnetic behavior of nanocomposites. This is of fundamental importance in the design of new magnetic materials with technological applications.