Superparamagnetic Hyperfine Relaxation in Zn 0.75 Ni 0.25 Fe 2 O 4
- PDF / 581,264 Bytes
- 4 Pages / 595.22 x 842 pts (A4) Page_size
- 28 Downloads / 193 Views
Superparamagnetic Hyperfine Relaxation in Zn0.75 Ni0.25 Fe2 O4 Hyunkyung Choi Department of Physics, Kookmin University, Seoul 02707, Korea
Hyung Joon Kim∗ Basic Materials & Chemicals R&D Center, LG Chem Research Park, Daejeon 34122, Korea (Received 31 March 2020; revised 6 May 2020; accepted 8 May 2020) We studied Zn0.75 Ni0.25 Fe2 O4 magnetic nanoparticles before and after plasma treatment by employing X-ray diffraction, magnetic measurements, hyperthermia measurements using the magneTherm device, and M¨ ossbauer spectroscopy. The M¨ ossbauer spectra of Zn0.75 Ni0.25 Fe2 O4 were recorded at various temperatures from 4.2 to 295 K. The M¨ ossbauer spectra for temperatures below the superparamagnetic transition temperature exhibited two sextets ascribed to tetrahedral and octahedral sites. Furthermore, the spectra demonstrated superparamagnetic behavior, as indicated by the doublet with zero hyperfine field at 295 K. The M¨ ossbauer spectra exhibited line broadening with increasing temperature, indicating superparamagnetic relaxation. The temperature dependence of the anisotropy energy was calculated based on the relaxation frequency. PACS numbers: 61.46.Df, 82.80. Ej, 87.50.yt Keywords: Anisotropy energy, Nanoparticles, M¨ ossbauer spectroscopy, Relaxation frequency, Superparamagnetic DOI: 10.3938/jkps.76.976
I. INTRODUCTION Ferrite nanoparticles have been widely studied due to their various applications in electromagnetic sensors, biomaterials, catalysts, and thermal treatments [1–5]. Magnetic ferrite nanoparticles have attracted significant attention owing to their various potential uses, and the studies conducted on them have contributed to the fundamental understanding of their properties, such as supermagnetism, and surface spin effects, which appear in particles with atomic-scale sizes [6–9]. The structure, particle size, and anisotropic hyperfine field fluctuations in ferrite nanoparticles play important roles in identifying their properties, such as hyperthermia, which may be useful in biomedicine [10, 11]. Although numerous studies on the physical properties of the nanoparticles of Zn-Ni ferrites have been performed, the mechanism underlying the paramagnetic phenomena induced by superparamagnetic relaxation remains relatively poorly studied. We previously reported [12] magnetic and heating efficiency measurements on Zn-Ni ferrite nanoparticles. Line broadening and pronounced paramagnetic phenomena were observed in the M¨ ossbauer spectra [13], which were attributed to the superparamagnetic relaxation. Notably, the line broadening occurred both before and after the plasma treatment of the nanoparticles ∗ E-mail:
[email protected]
pISSN:0374-4884/eISSN:1976-8524
because of the anisotropic hyperfine field fluctuations in the M¨ ossbauer hyperfine spectra [14–16]. In a previous study, the Zn content (x = 0, 0.25, 0.50, 0.75, and 1.0) [12] was varied for nanoparticles characterization whereas in this study, we investigated the composition with the highest magnetization and hyperthermia temperatures. We used plasma treatm
Data Loading...
