Distinct magnetic response of nanograined Zn1−xMnxO (x = 0, 0.02, 0.1) powders and thin films: Focus on the effect of the working atmosphere

Abstract

Nanocrystalline Zn1−xMnxO (where x = 0, 0.02, 0.1) powders and thin films were prepared by a polymeric precursor method and pulsed laser deposition, respectively. The wet chemistry method was chosen to synthesize the powders in order to improve key parameters as purity and grain-size distribution. Optimization procedures, encompassing substrate temperature, laser fluence and background gas conditions were performed and are intended to improve the crystalline quality of the films. X-ray diffraction studies reveal no clear evidence (within the detection limit of the technique) of affectation by impurities generated during the synthesis. Films prepared under optimized conditions feature a mosaic spread <0.3° and nearly bulk-like c-axis lattice parameter (5.198 Å). The substitution of Mn2+ cations in the tetrahedral sites of the wurtzite structure of pristine ZnO is confirmed both X-ray diffraction and Raman spectroscopy. Magnetic measurements, in turn, show that the powders are paramagnetic for temperatures above 3 K, while the thin films, grown in vacuum, are ferromagnetic at room temperature. These results indicate that variations in the preparation parameters have a marked influence on the magnetic responses of the Zn1−xMnxO system.