On the nucleation and growth of Zn1−xMnxO thin films grown by RF magnetron sputtering

Ferromagnetic behaviour of ZnO: the role of grain boundaries

“…This fact somehow coincides with the prediction of Dietl et al [1]. For example, in a number of works where s GB fell between s th for pure and manganese-doped ZnO, paramagnetic properties were observed in pure zinc oxide and ferromagnetic properties in manganese-doped samples [18–19]. As a result, s th increases with doping starting from pure ZnO.…”

Magnetization study of nanograined pure and Mn-doped ZnO films: Formation of a ferromagnetic grain-boundary foam

“…Thus, for example some authors whose samples had s GB between the values for pure and Mn-doped ZnO observed paramagnetism in pure ZnO and ferromagnetism in Mn-doped ZnO. 41,42 As proposed by Coey et al 17 Mn or Co dopants introduce into ZnO the shallow donor electrons which mediate the ferromagnetic exchange by forming bound magnetic polarons, which overlap to create a spin-split impurity band. However, it follows from Figs.…”

“…3-6͒ exhibit FM in many cases, while ZnO synthesized by wet chemistry methods or chemical vapor deposition ͑CVD͒ has intermediate properties; it can be either paramagnetic or FM. 2,[33][34][35][36][37][38][39][40][41][42] In order to quantify the defects and grain boundaries ͑GB͒ we introduced the specific GB area, s GB , the ratio of grainboundary area to volume, and determined it from published works devoted to the search of FM in pure and Mn-doped ZnO. In the case of single crystals 25,32,38 or doped ZnO films deposited on the ZnO single crystal, 54 no GBs are present, and since formally the s GB value is very large for them, the value s GB =4ϫ 10 2 m 2 / m 3 was chosen to indicate data for such single crystals close to the left margin in Fig.…”

“…1. If the polycrystals remain dense, but with elongated [2][3][4][5][6][7]15,22,38,42,46,53,[56][57][58][59] or flattened 44,48 grains ͑᭝, ᭡͒, the s GB value changes according to the aspect ratio usually quoted in published papers. In case of elongated grains s GB = 1.65a / D, D is the mean grain width and a Ͻ 1 is the aspect ratio ͑ratio of grain width to grain height͒.…”

Vacancy‐mediated room‐temperature ferromagnetism in Zn1−xMnxO thin films

“…Nevertheless, recent reports indicated that RTFM in Mn‐doped ZnO films are not only due to the magnetic ion doping but also due to the intrinsic point defects of the lattice 14–17. Recently, we have evaluated critical nucleation parameters and hence explained the FM in Zn 1− x Mn x O thin films 18.…”