Structural reconstruction and defects transition in mediating room temperature ferromagnetism in Co-doped ZnO film

Abstract

Room temperature (RT) ferromagnetism (FM) was achieved in H2/N2 annealed Co-doped ZnO films on silicon substrates and we got annealing temperature, Tan, dependence of saturation magnetization, Ms, which increased and finally reached a maximum as Tan elevated. The curve of Ms versus Tan seems like three steps. Surprisingly, after sequential oxygen annealing, Ms of each annealed film decreased abruptly at first, and then restored to its original order after the second annealing, which may owe to the formation of zinc-blende ZnO during thermal oxidation. This experiment illustrated that room temperature ferromagnetism in Co-doped ZnO films is associated with multiple factors.

Unexpected large room-temperature ferromagnetism in porous Cu2O thin films

“…Such devices typically make use of both spin and charge. The ferromagnetism observed in these compounds has been attributed to a variety of mechanisms including effects arising from transition metal ions, point defects, changes in the carrier concentration and grain boundaries [4][5][6][7][8][9][10][11]. Interestingly, ferromagnetism is also seen in some non-magnetic compound systems, such as pure HfO 2 films (about 5 Am 2 /kg) [12] and other nano-structures such as of ZnO films (about 1.0 emu/cm 3 ) [13] and pure TiO 2 powder (0.06 emu/g) [14].…”

“…Over the last decade, many groups have focused on doped, transition or rare earth, compound semiconductors such as Co:TiO 2 [4], Co:ZnO [5], Li:SnO 2 [6], and Cr:In 2 O 3 [7] due to their prospective applications in spintronic devices. Such devices typically make use of both spin and charge.…”

Effects of substrate temperature on the structural and magnetic properties in Cr-doped ZnO films prepared by magnetron sputtering

“…Recently, many researchers have demonstrated that the defects or oxygen vacancies (V o ) have significant influence on the room-temperature FM in TM doped ZnO films [26][27][28][29]. The FM is stronger in Zn 0.98 Cr 0.02 O film when the substrate temperature is 300°C, which is related to the increase of the number of defects and oxygen vacancies producted by the poor crystallization quality [30].…”

Sol–Gel Synthesis of Dy Co-Doped ZnO:V Nanoparticles for Optoelectronic Applications

“…It is known that the use of ZnO in new magneto-optical applications is difficult because of their diamagnetic and paramagnetic behaviors at room temperature. Room temperature ferromagnetism (RTFM) in ZnO has been reported to result from vacancy mediation [15][16][17]. Several works have been carried out to improve the RTFM in ZnO by substituting the Zn atom with dopants of transition metals and rare earths.…”