Ferromagnetism above Room Temperature Discovered in Mn-Doped ZnO
- PDF / 116,654 Bytes
- 1 Pages / 612 x 792 pts (letter) Page_size
- 54 Downloads / 207 Views
Ferromagnetism above Room Temperature Discovered in Mn-Doped ZnO Ferromagnetism at and above room temperature in magnetic semiconductors is a property of significant interest for spintronic applications and devices. Mn-doped ZnO and GaN have been predicted, based on theoretical calculations, to be potential candidates for exhibiting ferromagnetism above room temperature, leading to an intense search for the right material. The first observations of ferromagnetism above room temperature for dilute Mn-doped ZnO have now been reported. K.V. Rao, P. Sharma, and their colleagues from the Royal Institute of Technology (Sweden) and from the Armament Research Center (United States), Arizona State University (United States), University of Uppsala (Sweden), and the University of Sheffield (United Kingdom) report this discovery in both bulk and thin transparent films of Mn-doped ZnO in the October issue of Nature Materials. The incorporation of ferromagnetism in ZnO, a known piezoelectric and electro-optic material, may lead to various multifunctional properties. Doping ZnO with Mn, a 3d transition metal, can make possible the injection of a large amount of spins and carriers, making Mn-doped ZnO an excellent candidate for spintronic applications. In this study, the material was made by mixing appropriate amounts of ZnO and MnO 2 powders. The powder mixture was then calcined at 400°C for 8 h and then sintered at temperatures ranging from 500°C to 900°C for 12 h to obtain Zn1-x MnxO (x = 0.01, 0.02, and 0.1). For samples sintered below 700°C, superconducting quantum interference device measurements revealed ferromagnetic ordering. Elemental mapping using electron dispersive spectroscopy showed that the Mn was uniformly distributed and the material was homogeneous with a single phase. Sintering the samples above 700°C suppressed the ferromagnetism to below room temperature. This was attributed to the formation of Mn clusters, which are antiferromagnetic, and/or the formation of other phases. Ferromagnetic resonance (FMR) measurements indicated that the 2 at.% Mn-doped ZnO is a ferromagnetic semiconductor with a Curie temperature Tc well above 425 K. The researchers said that this is likely the first FMR measurement of room-temperature ferromagnetism in a semiconductor. Thin films of the Zn1-xMnxO were deposited on fused quartz substrates using a pulsed laser ablation technique. The films, which were transparent, also exhibited MRS BULLETIN/DECEMBER 2003
room-temperature ferromagnetism and phase homogeneity. High-resolution transmission electron microscopy on the thin films showed that the ZnO was ordered and oriented perpendicular to the a–b plane of a hexagonal lattice with a matching lattice parameter. The results suggest that the Mn substitutes for the Zn in the structure. This discovery of aboveroom-temperature ferromagnetism in Mndoped ZnO semiconductors opens up a number of possibilities for spintronic applications and novel magneto-optical components. GOPAL RAO
Large Diamond Crystals Grown at Low Temperatures Synthetic
Data Loading...
