High-temperature ferromagnetism in pulsed-laser deposited epitaxial (Zn, Mn) O thin films: Effects of substrate temperature (original) (raw)

Ferromagnetic behavior in Zn(Mn, P)O thin films

Physics Letters A, 2006

We present magnetic properties of Zn(Mn, P)O thin films, with 5 at% Mn, epitaxially grown by pulsed laser deposition in oxygen atmosphere on a-plane sapphire substrates. Ferromagnetism above room temperature was obtained for films with 0.1 at% P, grown at around 600 • C. Temperaturedependent magnetization curves indicate the presence of an antiferromagnetic coupling between the Mn magnetic moments. After annealing ferromagnetic films for 2 hours at 800 • C in N 2 atmosphere, they became paramagnetic at all temperatures.

Magnetic and optical properties of Zn1−xMnxO thin films prepared by pulsed laser deposition

Journal of Crystal Growth, 2006

We report on ferromagnetic characteristics of Zn 1Àx Mn x O thin films grown on Al 2 O 3 substrates by using pulsed laser deposition. The effects of oxygen pressure on the ferromagnetism in the Mn-doped ZnO thin films are discussed. The carrier concentration was found to be controlled by varying the oxygen pressure. By decreasing oxygen pressure, the films exhibited increases in both the lattice constant and fundamental band gap energy. Large magnetoresistance (MR) was observed in the film grown at 700 1C, especially over 10% in the positive MR. The results indicate the spin splitting caused by strong s-d exchange coupling between the conducting carriers and localized spins of Mn ions.

Magnetic and spectroscopic characteristics of ZnMnO system

2005

We report on the observation of room-temperature ferromagnetism in epitaxial (Zn, Mn) O films grown by a pulsed-laser deposition technique using high-density targets. The X-ray, microscopic, spectroscopic and magnetic properties of target material containing 6at.% of Mn and films were compared. The target shows the presence of large clusters exhibiting paramagnetic behavior.

Ferromagnetism in undoped ZnO grown by pulsed laser deposition

Materials Research Express, 2020

Undoped ZnO films grown on sapphire by pulsed laser deposition are magnetic at room temperature. A comprehensive study involving x-ray diffraction, positron annihilation spectroscopy, and superconducting quantum Interference device-vibrating sample magnetometer is performed to study the origin of the observed magnetization. Correlations between the saturation magnetization, VZn−2VO concentration and surface to volume ratio of the grain found experimentally show that the magnetization is associated with the vacancy cluster and probably VZn−2VO residing on the grain surface.

Ferromagnetism in epitaxial Zn 0.95 Co 0.05 O films grown on ZnO and Al 2 O 3

physica status solidi (a), 2006

Ferromagnetism in epitaxial Zn 0.95 Co 0.05 O films grown on .72. Vv, 75.50.Pp, 75.70.Ak, 81.05.Dz, 81.15.Fg In this article, the possible mechanisms resulting in strong ferromagnetic coupling in transition metal(TM)-doped ZnO and other diluted magnetic semiconductors (DMS) are reviewed and the prerequisites for the observation of room temperature ferromagnetism in TM-doped ZnO are defined. In order to study the ferromagnetic behavior we have grown epitaxial Zn 0.95 Co 0.05 O films simultaneously on (0001) ZnO and Al 2 O 3 substrates by laser molecular beam epitaxy at different deposition temperatures. A systematic study of the structural and magnetic properties has been performed to reveal their interdependence. Room temperature ferromagnetism has been found in Zn 0.95 Co 0.05 O films grown on ZnO, whereas for films deposited on sapphire only weak ferromagnetic signals have been detected which could not unambiguously be separated from those of the substrate. The different behavior is explained by different structural properties and defect densities in both films. Our experimental findings are in good agreement with a spin split impurity band model, where strong ferromagnetic exchange in ZnO : Co 2+ is obtained by a strong hybridization between the magnetic Co 2+ ion states and the donor states due to a large density of native defects. 3582 K. Nielsen et al.: Ferromagnetism in epitaxial Zn 0.95 Co 0.05 O films grown on ZnO and Al 2 O 3

Room temperature ferromagnetism in Mn ion implanted epitaxial ZnO films

Physica Status Solidi (a), 2006

Epitaxial ZnO films of ∼450 nm thicknesses were grown by MOCVD on r-sapphire and doped by implantation of 200 keV Mn ions to a dose of 5 × 1016 ions/cm2. The structural, chemical, and magnetic properties of the films were investigated with X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), X-ray absorption spectroscopy (XAS) and SQUID magnetometry. XRD and RBS show both Mn-doped ZnO and pure ZnO epitaxial layers in the as-implanted film, which is ferromagnetic at 5 K but nonmagnetic at room temperature. For the as-implanted materials, only Mn2+ ions are observed with XAS. Post-implantation annealing partially recovers the lattice damage and redistributes Mn into the entire ZnO film; in addition, Mn2+ ions are converted to a mixture of Mn3+ and Mn4+, and ferromagnetism is now observed above 300 K. Our results show that ion implantation is a viable route for achieving room temperature ferromagnetism in epitaxial ZnO films. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Room temperature ferromagnetic (Zn,Co)O epitaxial films obtained by low-temperature MOCVD process

Thin Solid Films, 2007

High quality epitaxial films of Zn 1 x Co x O solid solutions were obtained by low temperature MOCVD process using water vapor up to x 0.33. Depositions were carried out at 300°C on r sapphire substrates. Films structure and composition were investigated by XRD, XPS and EDX measurements. Magnetic properties were examined using SQUID and Kerr effect measurements. All samples showed ferromagnetic behavior at room temperature. NEXAFS and PES were employed to investigate electronic structure of the films.

Effect of oxygen pressure on the structural and magnetic properties of thin Zn 0.98 Mn 0.02 O films

The European Physical Journal Applied Physics, 2012

Thin Zn0.98Mn0.02O films were grown by pulsed laser deposition on glass substrates under oxygen pressure. The structural properties were studied by X-ray diffraction and Raman techniques, while the conductivity was characterized by the Hall effect. The oxygen pressure during the growth seems to govern the structural and the electrical properties of the thin Zn 0.98Mn0.02 films. In fact, the micron size grain and the resistivity of the Zn0.98Mn0.02O increase with the partial oxygen pressure. However, no evident effect was observed on the magnetic behavior. Electronic structure calculations were performed and magnetic moment carried by Mn atom was computed as well.

High-temperature ferromagnetism in Zn1-xMnxO semiconductor thin films

(2006) Journal of Magnetism and Magnetic Materials, 300 (2), pp. 407-411.

Clear evidence of ferromagnetic behavior at temperatures >400 K as well as spin polarization of the charge carriers have been observed in Zn 1-xMnxO thin films grown on Al 2O3 and MgO substrates. The magnetic properties depended on the exact Mn concentration and the growth parameters. In well-characterized single-phase films, the magnetic moment is 4.8 μB/Mn at 350 K, the highest moment yet reported for any Mn doped magnetic semiconductor. Anomalous Hall effect shows that the charge carriers (electrons) are spin-polarized and participate in the observed ferromagnetic behavior.