Abstract Ferrofluids based on magnesium substituted magnetite nanoparticles MgxFe3−xO4 (x = 0.1; 0.2; 0.4) were synthesised by a chemical co-precipitation method. Their physical properties have been compared with those of the magnetite based ferrofluid obtained by the same synthesis route. Both XRD and TEM studies showed particle size decrease with the increased Mg content while DLS experiments pointed to the more prominent aggregation of Mg-containing nanoparticles. Magnetic properties investigation conducted on the powder (i.e. dried) specimens showed decrease of magnetization values with increased Mg content except for the lowest concentration of x = 0.1 where substantial saturation magnetization rise of about 40% was recorded at room temperature. Heating abilities of the studied ferrofluids under the applied AC fields (SAR values) also showed decreasing trend with the increased Mg content even for x = 0.1 sample despite its elevated magnetization value. This trend has been understood as a consequence of the changed intrinsic nanoparticle properties such as size and magnetic anisotropy, as well as contribution of a collective behaviour due to an increased nanoparticle aggregation in Mg-doped systems.

中文翻译：

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共沉淀法制备的掺镁磁铁矿纳米粒子的磁性能和加热效率

摘要 通过化学共沉淀法合成了基于镁取代磁铁矿纳米颗粒 MgxFe3−xO4 (x = 0.1; 0.2; 0.4) 的铁磁流体。将它们的物理性能与通过相同合成路线获得的磁铁矿基铁磁流体的物理性能进行了比较。XRD 和 TEM 研究都表明，随着镁含量的增加，颗粒尺寸减小，而 DLS 实验表明含镁纳米颗粒的聚集更为突出。对粉末（即干燥）样品进行的磁性能研究表明，磁化值随着 Mg 含量的增加而降低，除了 x = 0.1 的最低浓度，其中在室温下记录到约 40% 的显着饱和磁化强度上升。尽管磁化值升高，但即使对于 x = 0.1 样品，所研究的铁磁流体在施加的交流场（SAR 值）下的加热能力也显示出随着 Mg 含量的增加而降低的趋势。这种趋势已被理解为改变固有纳米粒子特性（如尺寸和磁各向异性）的结果，以及由于 Mg 掺杂系统中纳米粒子聚集增加而导致的集体行为的贡献。