Ferromagnetic properties of the Mn-doped nanograined ZnO films

Abstract

Dense nanograined pure and Mn-doped Zn1−xMnxO polycrystals with x ranging between 0.1–34 at. % were synthesized by the wet chemistry method from butanoate precursors. Pure and Mn-doped ZnO possesses ferromagnetic properties only if the ratio of grain boundary (GB) area to grain volume sGB exceeds a certain threshold value sth. The polycrystals in this work satisfy these conditions and, therefore, reveal ferromagnetic properties. The observed dependence of saturation magnetization on the Mn concentration shows an unexpected nonmonotonous behavior. The increase in saturation magnetization at low Mn concentration is explained by the injection of divalent Mn2+ ions and charge carriers into pure ZnO. The decrease in saturation magnetization between 0.1 and 5 at. % Mn can be explained by the increase in the portion of Mn3+ and Mn4+ ions. The second increase in saturation magnetization above 5 at. % Mn is explained by the formation of multilayer Mn segregation layer in ZnO GBs. The shape of the dependence of saturation magnetization on Mn concentration is different for the Mn-doped nanograined ZnO manufactured by different methods. It is most probably controlled by the topology of GB network (ferromagnetic GB foam) in the ZnO polycrystals.

Role of interface in ferromagnetism of (Zn,Co)O films

“…2 and 3 that the magnitude of RT FM response relates to a large density of lattice defects (vacancies) at the interface region, as observed recently [8,9]. Firstly, deep defects concentration is very low in our ALD films grown at 4 Origin of RT FM in ZnCoO films grown at low temperature by ALD Several mechanisms were proposed to account for the RT FR of ZnCoO.…”

“…Further details on growth conditions can be found in Ref. [8]. Uniformity of ZnCoO samples was assessed by the secondary ion mass spectroscopy (SIMS, see Fig.…”

X-ray diffraction study on the microstructure of a Mg–Zn–Y alloy consolidated by high-pressure torsion

“…It is noted that oxide phase was not detected by X-ray diffraction either in the initial powder or in the consolidated specimens which can be explained by its small fraction (0.2-1% as calculated from the particle size and the oxide layer thickness) and/or its amorphous state. Additionally, the observation of this oxide phase is more difficult if it does not form dispersoids during sintering but rather remains in the form of a thin grain boundary layer, similar to carbides in steel after HPT [36] or MnO in Mn-doped nanograined ZnO [37].…”

Structural, optical and magnetic properties of Zn1−xMnxO micro-rod arrays synthesized by spray pyrolysis method

“…Although there are many experimental studies on magnetic and non-magnetic doped ZnO films showing room temperature ferromagnetism, the origin of ferromagnetism is still strongly debated in transition metal (TM)-doped oxide DMSs such as ZnO-based DMS [16][17][18]. Early studies proposed that a free carrier mediated mechanism was responsible for the ferromagnetic behavior [19].…”