Intrinsic ferromagnetism and magnetic anisotropy in Gd-doped ZnO thin films synthesized by pulsed spray pyrolysis method

Abstract

This paper reports an in-depth study on nanocrystalline Gd-doped ZnO thin films synthesized using versatile pulsed spray pyrolysis method and exhibit room temperature ferromagnetism. The detailed structural and microstructural studies confirm that the doped Gd ions occupy Zn sites and the peak shift can be elucidated by charge neutrality. Optical investigation shows that the Gd doping in ZnO lattice leads to a decrease in the near band edge position due to the introduction of new unoccupied states by Gd 4f electrons. The electronic structure of the Zn1−xGdxO at the O K edge shows the evolution of pre-edge spectral features similar to cuprates and manganites, and also confirms the strong hybridization of O 2p–Gd 4f/5d states. Furthermore, the Gd M5 edge provides evidence that Gd ions are in the trivalent state. Hysteresis measurements demonstrate that the Gd-doped ZnO films are magnetically anisotropic and exhibit intrinsic ferromagnetic behavior at room temperature. Higher magnetization in 3 kOe values is observed for a field applied perpendicular to the sample surface compared to the in-plane direction.

Homogeneous vertical ZnO nanorod arrays with high conductivity on an in situ Gd nanolayer

“…We also observed a shift in the (0002) XRD peak of the Gd-doped ZnO film towards higher angles compared to the undoped ZnO film, which was attributed to vacancies accompanying Gd incorporation into the crystal. 38 For samples deposited at P(O2) = 50 mTorr, this thin film peak overlaps with the NR peak located at a smaller 2 = 34.63  (Fig 1g). As the NR density increases with P(O2), the corresponding XRD peak at 2 = 34.39  becomes dominant, as shown for samples deposited at P(O2) = 100 and 200 mTorr.…”

“…Near edge X-ray absorption fine structure spectra at the O K-edge and Gd M5,4-edges indicated that Gd atoms replace Zn sites. 38,63 Therefore, the incorporation of Gd dopants creates a donor band below the conduction band maximum. Due to the donor band created near the CBM, a shift in the Fermi level occurs, and the material Please do not adjust margins Please do not adjust margins conductivity increases.…”

Identifying the influence of the intrinsic defects in Gd-doped ZnO thin-films

“…The shrinkage of c-parameter suggests the presence of an inclusion of vacancies that accompany Gd dopants in ZnO-a phenomenon that can arise due to crystal distortion during doping. 11 For Set 2 with varying P d , the c-parameter contracts with increasing P d (oxygen-rich environment), as shown in Figure 2(c). It should also be noted that, based on the RBS results, Gd concentration increases with increasing P d (Figure 2(a)).…”

“…In addition, Gddoped/implanted ZnO exhibited room temperature (RT) ferromagnetic behavior that has been attributed to defect/impurity bands mediated by Gd dopants. [7][8][9][10][11][12] Another interesting phenomenon that has been observed in Gd-doped ZnO is a Kondo-like effect, occurring due to a coupling between carriers and localized spin. 13 More specifically, the electrostatic tuning of Kondo effect in Gd-doped ZnO was demonstrated for electrical-double layer transistor applications.…”

“…13 More specifically, the electrostatic tuning of Kondo effect in Gd-doped ZnO was demonstrated for electrical-double layer transistor applications. 11 For ZnO materials, the trivalent RE 3þ ions are found to preferentially occupy substitutional or slightly displaced Zn sites. 11,12,14 However, thus far, few detailed investigations of the effect of growth conditions on the optical and structural properties of RE in situ doped ZnO have been carried out.…”