Abstract Magnetite has fascinated researchers for decades, due to its wide range of applications from spintronics to biomedicine. Despite a large body of works aimed at its magnetic properties, no consensus has been reached on the physical origin of the low temperature magnetic anomalies observed in magnetite. Although, a lot of work has been done in studying magnetite nanoparticles, but studies on the low temperature anomalies in those nanoparticles still remains unresearched. We report on the observation of the low temperature magnetic anomalies in highly crystalline, stoichiometric Fe3O4 nanorods and relate them to the coupled electron hopping relaxation process and domain wall motion. Both DC and AC susceptibility show the presence of a hump around 35 K, which is associated with the relaxation of Fe+2 extra electrons. Radio-frequency transverse susceptibility (TS) measurements indicated a noticeable increase in anisotropy field below ∼ 25 K, which is attributed to the rearrangement of Fe+2 electrons in the octahedral sites. TS experiments also revealed the domain wall freezing below ∼35 K. Our combined DC, AC and TS susceptibility studies shed light on the complex nature of the low-temperature magnetic behavior in nanostructured magnetite.

中文翻译：

---

与磁铁矿纳米棒中畴壁冻结和耦合电子跳跃相关的磁异常

摘要 几十年来，磁铁矿因其从自旋电子学到生物医学的广泛应用而吸引了研究人员。尽管有大量针对其磁性的工作，但尚未就磁铁矿中观察到的低温磁异常的物理起源达成共识。尽管在研究磁铁矿纳米粒子方面已经做了很多工作，但对这些纳米粒子的低温异常的研究仍未得到研究。我们报告了对高度结晶、化学计量的 Fe3O4 纳米棒中低温磁异常的观察，并将它们与耦合电子跳跃弛豫过程和畴壁运动联系起来。DC 和 AC 磁化率均显示在 35 K 附近存在驼峰，这与 Fe+2 额外电子的弛豫有关。射频横向磁化率 (TS) 测量表明，低于 25 K 时各向异性场显着增加，这归因于八面体位点中 Fe+2 电子的重排。TS 实验还揭示了约 35 K 以下的畴壁冻结。我们联合 DC、AC 和 TS 磁化率研究揭示了纳米结构磁铁矿中低温磁性行为的复杂性质。