Pannu, SavitaSavitaPannuDas, Subrat KumarSubrat KumarDasHalder, ParthaParthaHalderOrpe, P. B.P. B.OrpeKandada, Satya Prakash ReddySatya Prakash ReddyKandadaBalasubramanian, C.C.Balasubramanian2026-02-252026-02-252026-03-0110.1007/s00339-026-09310-x2-s2.0-105030169306https://repository.iitgn.ac.in/handle/IITG2025/34651In this work, mixed-phase iron oxide nanoparticles have been synthesized through a DC thermal arc plasma technique both in the presence and absence of an external magnetic field (MF). X-ray diffraction and electron microscope studies confirmed that γ-Fe₂O₃ is the dominant phase in all samples, accompanied by smaller fractions of Fe₃O₄ and α-Fe₂O₃. The magnetic field altered the phase evolution at higher current by promoting the formation of α-Fe at arc current of 100 A. The magnetic field modifies plasma dynamics and affects nanoparticle nucleation and growth producing smaller crystallites and narrower particle size distributions. Crystallite size reduced from ~ 22 nm (without MF) to ~ 10 nm in presence of MF for γ-Fe₂O₃. It leads to the development of preferentially spherical nanoparticle morphologies at higher arc currents. Magnetization measurements confirm ferrimagnetic behaviour for all samples. However, the magnetic field notably decreases the saturation magnetization compared to samples synthesized without field (66–73 emu/g). Coercivity increases with arc current under magnetic field-assisted synthesis. Retentivity values have been reduced for the samples processed under MF. These results are discussed in the light of the sharp temperature gradient of plasma and particle dynamics. These findings show that introducing an external magnetic field during arc plasma synthesis provides a powerful means to adjust the size, shape, phase composition, and magnetic characteristics of iron oxide nanoparticles, making the approach valuable for applications requiring precisely tailored magnetic responses.en-USfalseExternal magnetic field | Iron oxide nanoparticles | Magnetic properties | Thermal arc plasmaArticle14320630March 20260197arArticle