Ferromagnetism of cobalt-doped anatase TiO2 studied by bulk- and surface-sensitive soft x-ray magnetic circular dichroism

Abstract

We have studied magnetism in anatase Ti1−xCoxO 2−δ (x = 0.05) thin films with various electron carrier densities, by soft x-ray magnetic circular dichroism (XMCD) measurements at the Co L2,3 absorption edges. For electrically conducting samples, the magnetic moment estimated by XMCD was < 0.3 µB/Co using the surface-sensitive total electron yield (TEY) mode, while it was 0.3-2.4 µB/Co using the bulk-sensitive total fluorescence yield (TFY) mode. The latter value is in the same range as the saturation magnetization 0.6-2.1 µB/Co deduced by SQUID measurement. The magnetization and the XMCD intensity increased with carrier density, consistent with the carrierinduced origin of the ferromagnetism.Semiconductors partially substituted with magnetic ions are called diluted magnetic semiconductors (DMSs) and are expected to be useful in spintronics devices, where electron spins can be controlled by electric field and/or by photons. Ferromagnetic DMS's with Curie temperatures (T C 's) higher than room temperature are highly desirable for the development of spintronic devices. To date, much work in this area has been done, mainly on II-VI and III-V compounds doped with magnetic ions such as (Cd,Mn)Te [1] and (Ga,Mn)As [2,3], but their T C

XPS study of cobalt doped TiO2 films prepared by pulsed laser deposition

“…Spintronics devices are believed to have more advantages compared to traditional semiconductor devices, such as more compact size, multifunctional operation, faster processing speed and minimal heat dissipation. A promising diluted magnetic semiconductor has been Co‐doped TiO 2 , which has shown room temperature ferromagnetism that is tunable by an electric field . In TiO 2 ‐based magnetic semiconductors, the ferromagnetism is normally observed when the films have been deposited under low oxygen partial pressure.…”

(Invited) Room Temperature Ferromagnetism Induced by Electric Field in Cobalt-Doped TiO2

“…From the x-ray magnetic circular dichroism spectroscopy, a ferromagnetic response of Co 2+ ions was observed (17). Accordingly, any effect of the metallic segregation was ruled out as was also confirmed by scanning transmission electron microscope measurement (10).…”

Intrinsic versus extrinsic ferromagnetism inHfO2−xandNi:HfO2−Hildebrandt1, Yazdi2, Kurian3 et al. 2014Phys. Rev. B9030View full textAdd to dashboardCite

“…Ferromagnetism has been reported in many more materials, such as ZnO and TiO 2 , but also in perovskite materials [2,3]. In particular, in substituted ZnO and TiO 2 , ferromagnetic behavior was reported with T C > 300 K [4,5]. Other examples of materials with reported high-T C ferromagnetism are cerium and magnesium oxide doped with Co [6,7].…”