Photoluminescence and Raman studies for the confirmation of oxygen vacancies to induce ferromagnetism in Fe doped Mn:ZnO compound

• Comparison of magnetic property of ZnO, Zn0.98Mn 0.02O and Zn0.96(Mn0.02Fe0.02)O.
• Observation of enhanced magnetisation at room temperature in (Mn,Fe) doped ZnO.
• Raman and PL studies reveal presence of higher oxygen vacancy clusters.
• Electron Spin Resonance signal supports ferromagnetic state in the co doped sample.

With a motivation to compare the magnetic property, we synthesised undoped, transition metal (TM) Mn doped and (Mn:Fe) co-doped ZnO ceramics in the compositions ZnO, Zn0.98Mn0.02O and Zn0.96(Mn0.02Fe0.02)O. Systematic investigations on the structural, microstructural, defect structure and magnetic properties of the samples were performed. Low temperature as well as room temperature ferromagnetism has been observed for all our samples, however, enhanced magnetisation at room temperature has been noticed when ZnO is co-doped with Fe along with Mn. Particularly the sample with the composition Zn0.96Mn0.02Fe0.02O showed a magnetisation value more than double of the sample with composition Zn0.98Mn0.02O, indicating long range strong interaction between the magnetic impurities leading to higher ferromagnetic ordering. Raman and PL studies reveal presence of higher defects in form of oxygen vacancy clusters created in the sample due to Fe co doping. PL study also reveals enhanced luminescence efficiency in the co doped sample. Temperature dependent magnetisation study of this sample shows the spin freezing temperature around 39 K indicating the presence of small impurity phase of Mn2−xZnxO3 type. Electron Spin Resonance signal obtained supports ferromagnetic state in the co doped sample. Enhancement of magnetisation is attributed to interactions mediated by magnetic impurities through large number of oxygen vacancies created by Fe3+ ions forming bound magnetic polarons (BMP) and facilitating long range ferromagnetic ordering in the co- doped system.

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