On the defect induced ferromagnetic ordering above room-temperature in undoped and Mn doped ZnO thin films

• 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.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Materialteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering (hsv//eng)

Nyckelord

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

Materials science

Teknisk materialvetenskap

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