On the defect induced ferromagnetic ordering above room-temperature in undoped and Mn doped ZnO thin films
2009 (English)In: NOVEL MATERIALS AND DEVICES FOR SPINTRONICS / [ed] Sanvito S, Heinonen O, Dediu VA, Rizzo N, Warrendale, PA: MATERIALS RESEARCH SOCIETY , 2009, Vol. 1183, 3-8 p.Conference paper (Refereed)
Evidence for long range ferromagnetic order above room-temperature, RTFM, in pristine ZnO, In2O3, TiO2 nanoparticles and thin films, containing no nominal magnetic elements have been reported recently. This could question the origin of RTFM in doped dilute alloys if for example the ZnO matrix itself develops a defect induced magnetic order with a significant moment per unit cell. In this presentation we report a systematic study of the film thickness dependence of RTFM in pure ZnO deposited by DC Magnetron Sputtering. We observe a maximum in the saturation magnetization, Ms, value of 0.62 emu/g (0,018 ÎŒB/unit cell), for a -480 nm film deposited in an oxygen ambience of appropriate pressure. Above a thickness of around 1 ÎŒm the films are diamagnetic as expected. We thus see a sequential transition from ferromagnetism to para- and eventual diamagnetism as a function of film thickness in ZnO. We also find that in such a ZnO matrix with a maximum intrinsic defect induced moment, on doping with Mn the maximum enhanced Ms value of 0.78 emu/g is obtained for 1 at. % Mn doping. With this approach of appropriate doping in a defect tailored matrix, we routinely obtain RTFM in both undoped and Mn- doped ZnO thin films.
Place, publisher, year, edition, pages
Warrendale, PA: MATERIALS RESEARCH SOCIETY , 2009. Vol. 1183, 3-8 p.
, Materials Research Society Symposium Proceedings, ISSN 0272-9172 ; 1183
Dc magnetron sputtering, Dilute alloys, Ferromagnetic orderings, Induced magnetic order, Intrinsic defects, Long range ferromagnetic order, Magnetic elements, matrix, Mn-doped ZnO, Mn-doping, Per unit, Pure ZnO, Room temperature, Significant moments, Systematic study, TiO, Unit cells, ZnO, ZnO matrix, Defects, Diamagnetism, Doping (additives), Ferromagnetic materials, Ferromagnetism, Magnetic films, Manganese, Manganese oxide, Metallic films, Nanomagnetics, Optical films, Oxygen, Saturation magnetization, Thin films, Zinc oxide
IdentifiersURN: urn:nbn:se:kth:diva-14174ISI: 000284863300001ScopusID: 2-s2.0-77950964230OAI: oai:DiVA.org:kth-14174DiVA: diva2:331415
Symposium on Novel Materials and Devices for Spintronics San Francisco, CA, APR 14-17, 2009
QC 201007222010-07-222010-07-222011-01-04Bibliographically approved