Berquó Thelma S, Erbs Jasmine J, Lindquist Anna, Penn R Lee, Banerjee Subir K
Institute for Rock Magnetism, Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455, USA. Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA.
J Phys Condens Matter. 2009 Apr 29;21(17):176005. doi: 10.1088/0953-8984/21/17/176005. Epub 2009 Apr 1.
The effects of magnetic interactions in the magnetic properties of six-line ferrihydrite particles were investigated by studying the behavior of aggregated versus coated particles. Four different coating agents (sugar, alginate, lactate and ascorbate) were employed in order to obtain dispersed particles and prevent particle agglomeration; one sub-sample was allowed to dry with no coating agent. The five sets of ferrihydrite particles were from the same batch and the size was estimated as 3.6 ± 0.4 nm in length. Low temperature magnetization, ac susceptibility and Mössbauer spectroscopy data showed contrasting blocking temperatures for uncoated and coated samples with a decrease of T(P) from about 50 K to 12 K, respectively. The contributions from magnetic interactions were recognized in magnetic measurements and the effective anisotropy constant for non-interacting ferrihydrite was estimated as (100 ± 10) × 10(3) J m(-3). Overall, employing sugar and alginate as coating agents was more successful in preventing particle aggregation and magnetic interactions. In contrast, ascorbate and lactate were unsuitable due to the chemical reaction between the coating agent and ferrihydrite surface.
通过研究聚集颗粒与包覆颗粒的行为，研究了六线水铁矿颗粒磁性中磁相互作用的影响。使用了四种不同的包覆剂（糖、藻酸盐、乳酸盐和抗坏血酸盐）以获得分散颗粒并防止颗粒团聚；一个子样品在没有包覆剂的情况下干燥。这五组水铁矿颗粒来自同一批次，估计长度为3.6±0.4纳米。低温磁化、交流磁化率和穆斯堡尔谱数据显示，未包覆和包覆样品的阻塞温度形成对比，T(P)分别从约50K降至12K。在磁测量中识别出了磁相互作用的贡献，非相互作用水铁矿的有效各向异性常数估计为(100±10)×10(3)J m(-3)。总体而言，使用糖和藻酸盐作为包覆剂在防止颗粒团聚和磁相互作用方面更为成功。相比之下，抗坏血酸盐和乳酸盐由于包覆剂与水铁矿表面之间的化学反应而不合适。
