Microstructure, ferromagnetism, and magnetic transport of Ti1−xCoxO2 amorphous magnetic semiconductor

Abstract

Ti O 2 -based magnetic semiconductors with high Co doping concentrations (Ti1−xCoxO2) were synthesized under thermal nonequilibrium condition by sputtering machine. Microstructure and composition analysis by transmission electron microscopy, x-ray photoelectron spectroscopy, and electron energy-loss spectroscopy indicated that Co element was incorporated into TiO2 to form Ti1−xCoxO2 compound. The direct evidence for the compositional inhomogeneity of the Ti1−xCoxO2 compound was given. Room temperature ferromagnetism with high magnetization was obtained, which could be attributed to the intrinsic properties of the amorphous magnetic semiconductor. The electrical transport in a low temperature range was explained by spin-dependent Efros’s variable range hopping, and correspondingly an exponential function of the magnetoresistance versus T−1∕2 was found.

Oxygen Deficiency and Room Temperature Ferromagnetism in Undoped and Cobalt-Doped $\hbox{TiO}_{\bm 2}$ Nanoparticles

“…The metallic Co 2p 3/2 peak occurs at 778 eV [42] but in Fig. 7, no such peak was observed and the energy difference between Co 2p 3/2 and Co 2p 1/2 is 15.5 eV, which excludes the possibility of the formation of Co metal clusters, because the energy difference for Co metal clusters is 15.05 eV [46]. On the other hand, if Co is surrounded by oxygen, these differences should be 15.5 eV [42].…”

Room-temperature ferromagnetism observed in Mo-doped indium oxide films

“…Interest in ferromagnetism in normally nonmagnetic semiconducting materials was triggered by the theoretical prediction of room-temperature ferromagnetism in various dilute magnetic semiconductors. 1 The possibility of ferromagnetism in oxides film [2][3][4] has attracted a great deal of interest following the report of ferromagnetism in Co doped TiO 2 .…”

Stoichiometry determined exchange interactions in amorphous ternary transition metal oxides: Theory and experiment

“…Furthermore, no cobalt cluster has been observed in our samples, in agreement with the experimental observation. 8,30,31 The Co 42 Zn 42 O 84 shows the similar microstructure, with a higher proportion of cobalt-rich regions.…”