Magnetic and electron spin resonance studies of W doped CoFe2O4 polycrystalline materials

Magnetic and electron spin resonance studies of W doped CoFe2O4 polycrystalline materials

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We report the magnetic and electron spin resonance (ESR) properties of W doped CoFe2O4 polycrystalline materials, prepared by standard solid-state reaction method.W was doped (0-15%) in CFO lattice on Fe site.Isothermal magnetization measurements RAPID MASS CREAMY VANILLA reveal that the coercive field (Hc) (1300-2200 Oe) and saturation magnetization MS (35-82 emu/g) vary strongly as a function of W doping at all the temperatures (4-300 K) measured.We believe that a strong decrease in magnetic anisotropy in CFO after doping with W could cause a decrease in Hc.Up on doping CFO with W in place of Fe, the process transforms part of Fe3+ into Fe2+ due to the creation of more oxygen vacancies.

This hinders the super-exchange interaction between Fe3+ and Fe2+, which causes a decrease in MS.Zero-field cooled (ZFC) Straps and field cooled (FC, 1000 Oe) magnetization responses measured at 4 K on 1% W doped CFO show no indication of exchange bias, inferring that there are no other microscopic secondary magnetic phases (no segregation).This observation is corroborated by ESR (9.398 GHz) measurements collected as a function of temperature (10-150 K) and W doping (0-15%).We find that ESR spectra did not change after doping with W above 0.

5%.However, ESR spectra collected from 0.5% W doped CFO sample showed a strong temperature dependence.We observed several ESR signals from 0.5% W doped CFO sample that could be due to phase separation.