Structural and magnetic analysis of epitaxial films of Gd-doped ZnO

Abstract

Zn (1−x) Gd x O epitaxial films prepared by reactive magnetron sputtering were studied using a combination of synchrotron based x-ray absorption spectroscopies, x-ray diffraction, and classical magnetometry. With nominal Gd concentrations of up to 16% only paramagnetism is found. Reducing the oxygen content in the sputter gas provokes phase separation, however, the samples remain paramagnetic. The experimental findings are corroborated by first-principles density-functional theory calculations. In all cases a paramagnetic behavior is found with Gd atomic moments comparable to the experiment. The structural degradation with increasing Gd concentration is consistently found by experiment as well as theory.

Magnetic Properties of Gadolinium-Doped ZnO Films and Nanostructures

“…Even though magnetic behavior is generally reported in Gd-doped ZnO thin films, these studies failed to obtain longrange FM in Gd-doped ZnO, perhaps due to severe distortion in the crystal as a result of ion implantation damage, to the high Gd dopant concentration (>2 at%), or to the use of latticemismatched substrates [15][16][17][18][19][20][21]. Paramagnetism has also observed at high concentrations of Gd [21]. This is associated with the precipitation of Gd atoms at higher concentrations, leading to structural degradation.…”

“…All in situ Gd-doped wurtzite ZnO thin films were grown by pulsed laser deposition (PLD) on lattice-matched a-sapphire (Al 2 O 3 ) substrate (0.08% lattice mismatch between [11][12][13][14][15][16][17][18][19][20][21] aAl 2 O 3 and (0 0 0 1) c-ZnO). When the lattice mismatch was minimized, good quality films could be produced as structural defects in which line defects were substantially reduced.…”

Magnetic and Electrical Properties of Undoped and Holmium Doped ZnO Thin Films Grown by Sol-Gel Method

“…The 4f electrons are localized and the exchange interactions are indirect via conduction electrons, which result in high total magnetic moments per atom owing to its high orbital momentum [16]. Rare earths such as Gd [16,[22][23][24], Tb [19,25], Er [17], Eu [26], and Sm [20] were used as dopants in order to modify the ZnO magnetic properties.…”

Ferromagnetism in Gd doped ZnO nanowires: A first principles study

“…However, the existing experimental results are controversial and depend strongly on the doping method and the defect type. [10][11][12]15 In addition, the mechanism and origin of the magnetic coupling are poorly understood. The few theoretical studies that have been conducted thus far deal with RE doping in bulk ZnO and do not elucidate the mechanisms responsible for RTFM in Gd-doped wurtzite ZnO nanostructures.…”

“…15 In this scenario, doping with Gd seems to be a promising way to achieve RTFM in ZnO nanostructures. However, the existing experimental results are controversial and depend strongly on the doping method and the defect type.…”