Magnetic and electric properties are investigated for the nanosized YMnO3 samples with different grain sizes (25 nm to 200 nm) synthesized by a modified Pechini method. It shows that magnetic and electric properties are strongly dependent on the grain size. The magnetic characterization indicates that with increasing grain size, the antiferromagnetic (AFM) transition temperature increases from 52 to 74 K. A corresponding shift of the dielectric anomaly is observed, indicating a strong correlation between the electric polarization and the magnetic ordering. Further analysis suggests that the rising of AFM transition temperature with increasing grain size should be from the structural origin, in which the strength of AFM interaction as well as the electrical polarization is dependent on the in-plane lattice parameters. Furthermore, among all samples, the sample with grain size of 95 nm is found to have the smallest leakage current density (< 1 μA/cm2).PACS: 75.50.Tt, 75.50.Ee, 75.85.+t, 77.84.-s

High-quality orthorhombic (OT) TmMnO3 (TMO) thin films with a-axis perpendicular to the film surface are grown epitaxially on Nb-doped SrTiO3(110) substrates using pulsed laser deposition. The structural, magnetic, and electric properties of OT-TMO films are measured. We found that a strong coupling between the magnetic structure and the electric polarization. Our experimental results also show that ferroelectricity in OT-TMO thin films below 32 K. Furthermore, the large electric polarization up to 0.45 μC/cm2 is observed at 10 K, supporting a theoretical prediction of large polarization in the E-type spin structure in this system.

The crystallinity and intrinsic defects of transparent conducting oxide (TCO) films have a high impact on their optical and electrical properties and therefore on the performance of devices incorporating such films, including flat panel displays, electro-optical devices, and solar cells. The optical and electrical properties of TCO films can be modified by tailoring their deposition parameters, which makes proper understanding of these parameters crucial. Magnetron sputtering is the most adaptable method for preparing TCO films used in industrial applications. In this study, we investigate the direct and inter-property correlation effects of sputtering power (PW) on the crystallinity, intrinsic defects, and optical and electrical properties of Al-doped ZnO (AZO) TCO films. All of the films were preferentially c-axis-oriented with a wurtzite structure and had an average transmittance of over 80% in the visible wavelength region. Scanning electron microscopy images revealed significantly increased AZO film grain sizes for PW ≥ 150 W, which may lead to increased conductivity, carrier concentration, and optical band gaps but decreased carrier mobility and in-plane compressive stress in AZO films. Photoluminescence results showed that, with increasing PW, the near band edge emission gradually dominates the defect-related emissions in which zinc interstitial (Zni), oxygen vacancy (VO), and oxygen interstitial (Oi) are possibly responsible for emissions at 3.08, 2.8, and 2.0 eV, respectively. The presence of Zni- and Oi-related emissions at PW ≥ 150 W indicates a slight increase in the presence of Al atoms substituted at Zn sites (AlZn). The presence of Oi at PW ≥ 150 W was also confirmed by X-ray photoelectron spectroscopy results. These results clearly show that the crystallinity and intrinsic-defect type of AZO films, which dominate their optical and electrical properties, may be controlled by PW. This understanding may facilitate the development of TCO-based optoelectronic devices for industrial production.

This article aims to investigate the Raman modes present in Mn-doped ZnO thin films that are deposited using the magnetron co-sputtering method. A broad band ranging from 500 to 590 cm −1 is present in the Raman spectra of heavily Mn-doped ZnO films. The multi-peak-fitting results show that this broad band may be composed of six peaks, and the peak at 528 cm −1 could be a characteristic mode of Mn 2 O 3 . The results of this study suggest that the origin of the Raman peaks in Mn-doped ZnO films may be due to three major types: structural disorder and morphological changes caused by the Mn dopant, Mn-related oxides and intrinsic host-lattice defects.

Magnetron dc cosputtering of a composite target of graphite disk plus iron rods was used in manufacturing carbon films with Fe 3 C nanograin inclusions. Both temperature-and field-dependent magnetizations, M (T) and M (H), were measured for samples of various carbon concentrations ͑from 37% to 85%͒. M (T) were measured in both conditions of zero-field cooling and a field cooling at Hϭ100 Oe. Experimental results of (T), obtained from M (T), of zero-field cooling, were theoretically fitted by using Wolhfarth's model of noninteracting particles with log-normal distribution function of particle size.