Impact of Cr doping on the structure, optical and magnetic properties of nanocrystalline ZnO particles

• Published in: Journal of alloys and compounds 2023-10, Vol.960, p.170815, Article 170815
• Main Authors: Lokesha, H.S., Prinsloo, A.R.E., Mohanty, P., Sheppard, C.J.
• Format: Article
• Language: English
• Subjects: Combustion synthesis; Electron paramagnetic resonance; Ferromagnetism; Photoluminescence; ZnO:Cr
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2023.170815

The doping of Cr ions on the structure, optical and magnetic properties of ZnO have been investigated. Zn1−xCrxO (0 ≤ x ≤ 0.05) samples were prepared by the solution combustion method. Rietveld refined x-ray diffraction results reveal that all the samples are in a hexagonal structure. Transmission electron microscopy (TEM) revealed that the particle size was 48.2 ±2.1 nm, 29.4 ± 2.2 nm and 25.3 ± 2.1 nm for the Zn1−xCrxO with x = 0, 0.03 and 0.05, respectively. The band-gap decreases slightly from 3.308 ± 0.003 eV to 3.291 ± 0.003 eV with increase of Cr content from x = 0 to 0.05, respectively. The field-dependent magnetization M(μοH) measurements of ZnO and Cr-doped ZnO exhibit room temperature ferromagnetism (RTFM). Photoluminescence and electron paramagnetic resonance exhibits negatively charged zinc vacancies (VZn−) and singly ionized oxygen vacancies (Vo+) in ZnO and these defects are responsible for RTFM. And the VZn− accountable for RTFM in Cr-doped ZnO. EPR results confirmed that Cr3+ ions replaces the Zn2+ sites in the hexagonal ZnO. The observed long-range ferromagnetism ordering is explained based on the bound magnetic polaron (BMP) mechanism. This work elucidates the origin of RTFM in synthesized ZnO and Cr-doped ZnO. •Rietveld refined XRD results confirm Zn1−xCrxO samples are in a hexagonal phase.•Defects in the samples are analyzed using photoluminescence and EPR studies.•The presence VZn− and Vo+ are the main reason for the origin of RTFM in undoped ZnO.•EPR results confirmed that Cr3+ ions replace the Zn2+ sites in the hexagonal crystal structure.•The BMPs interaction mediated by the Cr is accountable for the RTFM in Cr-doped ZnO.