Spin-polarized carriers and ferromagnetism induced by Pt incorporation in ZnO: an experimental and DFT assessment

Abstract

In the present work, we report the synthesis and detailed investigation on the structural, microstructural, and magnetic properties of ZnO–xPt (x = 0.0, 0.02, 0.06, 0.10 wt%) nanocomposites, using experimental and theoretical approaches. The structural analysis, using Rietveld-refined X-ray diffraction patterns, shows that all samples exhibit a wurtzite phase with a hexagonal structure and a P6₃mc symmetry. Transmission electron microscopy analysis revealed a consistent morphology for different Pt percentages, with nanoparticle diameters consistently less than 100 nm. Room-temperature magnetic measurements revealed superparamagnetic behavior, with the saturation magnetization increasing with the Pt percentage. However, the loops exhibited open regions in the low magnetic field range, where the remanent magnetization and coercivity also increased with the Pt weight percentage. The magnetic behavior is partly attributed to the bound magnetic polaron mechanism, and Thamm–Hesse analysis ruled out significant interparticle interactions, suggesting that clustering is not the dominant contribution. Density functional theory calculations indicate that Pt incorporation at Zn sites is energetically stable, regardless of the presence of oxygen vacancies. Spin-density isosurfaces reveal localized magnetic moments around Pt and adjacent oxygen atoms. The projected density of states exhibits a transition from semiconducting to half-metal behavior, producing spin-polarized carriers that can mediate long-range magnetic interactions. The close agreement between experimental observations and theoretical predictions highlights low-concentration Pt-doped ZnO as a promising nanoscale material for spintronic applications.