Effects of rapid thermal annealing on the ferromagnetic properties of sputtered Zn1−x(Co0.5Fe0.5)xO thin films

Abstract

We have investigated the effects of rapid thermal annealing under vacuum on the CoFe-doped ZnO [Zn1−x(Co0.5Fe0.5)xO] films grown by reactive magnetron co-sputtering. At least up to x=0.15, the films have the single phase of the same wurtzite structure as pure ZnO. Ferromagnetism was observed for the CoFe-doped ZnO films. We found that rapid thermal annealing leads to a remarkable increase in the spontaneous magnetization of the CoFe-doped ZnO as well as the electron concentration. The annealing also leads to a significant increase in the Curie temperature (TC), resulting in room temperature ferromagnetism with TC>300 K for the CoFe-doped ZnO films.

Magnetic oxide semiconductors

“…>300-350K [29,30] --->300K [30,32] 2 K [83] -4 (10) 2002 ---45K [33] >300K with Co [88] 550K with Cu [89] >350K [62,64] >300K with Fe [88] with Fe [89] 5 (10) 2003 --->r.t.…”

Dose dependence of ferromagnetism in Co-implanted ZnO

“…In addition to cobalt, other 3d transition elements have also been used for doping, including Mn, 5,15,[20][21][22] Ni, 5,11,15 V, 11,15,23 Cr, 5,11 and also Fe. 5,11,15,24 Various solubility limits for Co in ZnO were reported by different groups. Prellier et al 10 determined a solubility limit of about 10 at.…”

Surface modification of Co-doped ZnO nanocrystals and its effects on the magnetic properties

“…Some groups have reported ferromagnetism in transition metal doped ZnO systems with Curie temperatures T C ranging from 30 to 550 K, [3][4][5][6][7][8][9][10][11][12][13] while others have found antiferromagnetic, spin glass, or paramagnetic behavior. [14][15][16][17][18][19] Thus, the topic is still controversial and further investigations are needed to clarify these materials' magnetic properties that are very sensitive to the preparation method.…”