Effects of DC magnetic field in the range of 0–180 mT on the properties of cobalt oxide nanoparticles (Co 3 O 4 NPs) synthesized by pulse laser ablation method in distilled water has been investigated. Ablation was carried out in the presence of permanent magnets with variable strengths. Significant blue shift in excitonic absorption peaks of produced nanoparticles show that with increasing the magnetic field strength during the ablation process, size of nanoparticles was decreased noticeably. This result was confirmed by SEM and TEM images. XRD pattern show that with applying external magnetic field we may have crystalline structure nanoparticles while in the absence of external magnetic field, only amorphous phase of Co nanoparticles was produced. FTIR spectra present the metal oxygen vibration at 614 and 668 cm −1 , revealed octahedral and tetrahedral site of cobalt oxide system. In overall it can be concluded that external magnetic field is a strong tool to control the properties of laser ablation produced ferromagnetic nanoparticles.

中文翻译：

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外磁场对脉冲激光烧蚀制备钴纳米粒子特性的影响

研究了 0-180 mT 范围内的直流磁场对通过脉冲激光烧蚀法在蒸馏水中合成的氧化钴纳米粒子（Co 3 O 4 NPs）性能的影响。在具有可变强度的永磁体存在的情况下进行消融。产生的纳米粒子激子吸收峰的显着蓝移表明，随着烧蚀过程中磁场强度的增加，纳米粒子的尺寸显着减小。该结果由 SEM 和 TEM 图像证实。XRD图谱表明，在施加外部磁场的情况下，我们可能具有晶体结构的纳米颗粒，而在没有外部磁场的情况下，仅产生了非晶相的 Co 纳米颗粒。FTIR 光谱显示了 614 和 668 cm -1 处的金属氧振动，揭示了氧化钴系统的八面体和四面体位点。总的来说，可以得出结论，外部磁场是控制激光烧蚀产生的铁磁纳米粒子的特性的有力工具。