Effect of Ni doping on the microstructure and high Curie temperature ferromagnetism in sol-gel derived titania powders

Nupur Bahadur, Renu Pasricha, Govind, Suresh Chand, Ravinder Kumar Kotnala

Research output: Contribution to journalArticlepeer-review

Abstract

Undoped, 0.05 and 0.5 mol% Ni-doped TiO 2 powders were prepared by a modified sol-gel route. The doping effects on the microstructure and magnetism for the powdered samples have been systematically investigated. Doping of Ni in TiO 2 inhibited rutile crystal growth. The probable reason for this is discussed on the basis of band calculation based analysis of electronic structures of 3d transition metal-doped TiO 2 and the energetic, transformation kinetics and phase stability of anatase over rutile as the function of particle size. Room temperature ferromagnetism (RTFM) with the saturation magnetization of 12 m emu g -1 and Curie temperature as high as 820 K is observed only in case of 0.05 mol% Ni:TiO 2 powdered sample, whereas undoped TiO 2 was diamagnetic and 0.5 mol% Ni:TiO 2 was paramagnetic in nature. The role of any magnetic impurity or any Ni metal in the origin of the RTFM has been ruled out by energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and high resolution TEM (HRTEM) analysis, whereas magnetic force microscopy (MFM) established the presence of magnetic domains, supporting the intrinsic diluted magnetic semiconductor behavior. The observed ferromagnetism has been attributed to the spin ordering through exchange interaction between holes trapped in oxygen orbitals adjacent to Ni substitutional sites.

Original languageEnglish (US)
Pages (from-to)471-479
Number of pages9
JournalMaterials Chemistry and Physics
Volume133
Issue number1
DOIs
StatePublished - Mar 15 2012

Keywords

  • Magnetic force microscopy (MFM)
  • Magnetic properties
  • Oxides
  • Sol-gel growth

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics

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