Semiconducting and ferromagnetic behavior of sputtered Co-doped TiO2 thin films above room temperature

Abstract

We have investigated Co-doped TiO2 thin films grown by reactive co-sputtering. X-ray diffraction showed a single phase polycrystalline rutile structure, without any segregation of Co into particulates within the instrumental resolution limit. The atomic content of Co ranged from 1% to 12%. The temperature dependence of resistivity showed an extrinsic semiconducting behavior. From optical absorption measurements, the band gap Eg≈3.25±0.05 eV was found, independent of the Co concentration, and in agreement with a literature value. Room temperature M-H loops showed a ferromagnetic behavior for Co content higher than 3%. The magnetic moment per Co atom was estimated to be about 0.94 μB, suggesting a low spin configuration of Co ions. The temperature dependence of remanent magnetization revealed a Curie temperature higher than 400 K for Co content of 12%.

Microstructural Investigation, Raman and Magnetic Studies on Chemically Synthesized Nanocrystalline Ni-Doped Gadolinium Oxide (Gd1.90Ni0.10O3−δ)

“…1,2 In the family of DMS systems, room temperature ferromagnetism (RTFM) in transition metal (TM) ion-doped ZnO, SnO 2 , TiO 2 , CeO 2 etc. [3][4][5][6][7][8] have been observed by various researchers. In addition, dilute magnetic dielectrics (DMDs) are also an important area of research due to their enhanced magnetic property at room temperature (RT) and high dielectric constant.…”

Модификация Кобальтом Тонких Пленок Рутила При Магнетронном Распылении И Вакуумном Отжиге

“…В ряде работ показано, что плен-ки оксида титана, легированные кобальтом, проявляют ферромагнитный отклик при комнатной температуре и выше [1][2][3]. В литературе приводятся данные по магнетизму рутила, имплантированного кобальтом [4,5], согласно которым в системе имеет место формирование двух магнитных фаз: магнитные наночастицы металли-ческого кобальта как на поверхности, так и в объеме образца, и твердые растворы, в которых парамагнитные Co 2+ -ионы изоморфно замещают ионы Ti 4+ в матрице TiO 2 [6].…”

Electronic structure and x-ray magnetic circular dichroism of Mn-doped TiO2

“…The transition-metal-doped (V, Cr, Fe, Ni, etc.) TiO 2 alloys have been under numerous experimental and theoretical investigations [6][7][8][9][10][11][12] on their magnetic properties and the related structural and electronic properties since the discovery of room-temperature ferromagnetism in Co-doped anatase TiO 2 thin films [13]. Despite the intensive research on TiO 2 -based magnetic oxides, the interpretations for the observed ferromagnetic (FM) properties have often been controversial, e.g., on whether the exhibited ferromagnetism is intrinsic or not [12].…”