A key to room-temperature ferromagnetism in Fe-doped ZnO: Cu

Abstract

Successful synthesis of room-temperature ferromagnetic semiconductors, Zn$_{1-x}$Fe$_{x}$O, is reported. The essential ingredient in achieving room-temperature ferromagnetism in bulk Zn$_{1-x}$Fe$_{x}$O was found to be additional Cu doping. A transition temperature as high as 550 K was obtained in Zn$_{0.94}$Fe$_{0.05}$Cu$_{0.01}$O; the saturation magnetization at room temperature reached a value of $0.75 \mu_{\rm B}$ per Fe. Large magnetoresistance was also observed below $100 $K.Comment: 11 pages, 4 figures; to appear in Appl. Phys. Let

Lattice location and thermal stability of implanted Fe in ZnO

“…In the case of ZnO, besides V, Cr, Mn, Co and Ni, Fe should also act as a ferromagnetic dopant [3][4][5]. Several reports on ferromagnetic systems based on ZnO can be found in the literature [1,[6][7][8][9][10][11][12][13][14]. Cases in which no ferromagnetic behavior was observed [7,[15][16][17][18] revealed systematic trends for the various transition metals, doping concentrations, and differences between n-and p-type ZnO, but also conflicting results between different authors.…”

“…The exact nature of the ferromagnetism also remains unclear [1,8,11,13]; among possible problems are the formation of metallic TM or TM-oxide clusters [9,[12][13][14]17] or magnetism from the substrate on which thin films are deposited [18]. Two recent review papers on the subject concluded that a more precise control of the TM dopant in the oxide and careful structural and microstructural analyses are needed [1,11].Experimentally TM dopants have been introduced both during ZnO powder synthesis [10,14,16] and growth of epitaxial thin films [6][7][8][9]11,15,18]. In addition, ion implantation is also actively being explored for TM doping of ZnO [1,12,13,19].…”

“…Experimentally TM dopants have been introduced both during ZnO powder synthesis [10,14,16] and growth of epitaxial thin films [6][7][8][9]11,15,18]. In addition, ion implantation is also actively being explored for TM doping of ZnO [1,12,13,19].…”

The Magnetic Properties of Zn<sub>0.98</sub>Fe<sub>0.02</sub>O with Additional Cu Doping

“…Room-temperature ferromagnetism in ZnO doped with Fe has been achieved; however, there remain some questions regarding the origin of the magnetic behavior in Fe-doped ZnO materials. It is deemed that additional Cu doping is essential to achieve RTFM in Fe-doped ZnO bulk samples [3]. Howerver, Shim et al found that the ferromagnetism in Feand Cu-codoped ZnO stems from the secondary phase ZnFe 2 O 4 [4].…”

Lattice location and stability of implanted Cu in ZnO

“…Apart from its possible influence on the optical properties of ZnO, Cu has recently been found a suitable codopant in order to activate room-temperature ferromagnetism in Zn 0.94 Fe 0.05 Cu 0.01 O, 12 other applications of Cu in ZnO include varistor 13 and piezoelectric 14 devices. In these three cases the beneficial role of Cu is presumably related to the formation of electrically active Cu acceptors.…”