Effect of annealing temperature on the structural, electronic and magnetic properties of Co doped TiO2 nanoparticles: An investigation by synchrotron-based experimental techniques

Origin of Enhancement of Orbital Magnetic Moment in SiO2-Coated Fe3O4 Nanocomposites Studied by X-ray Magnetic Circular Dichroism

“…Figure indicates that there is no such significant shifting found in the spectra of S-0 as considered with other SiO 2 -coated S-1, S-2, S-3, S-4, and S-5 samples except a decrement in the t 2g /e g ratio signifying the changes occurred at the local environment. The features indicated as A, B, and C are found to exhibit similarity with the XAS spectral features of Fe 3 O 4 published previously. ,,,− The spectral feature specified as A at the pre-edge (below ∼532 eV) indicates the transition from the unoccupied states of O 1s to O 2p–Fe 3d hybridized states, specifying chief localization at Fe sites. The prepeak of the samples split in two peaks A 1 and A 2 with energy regions at 530.4 and 531.5 eV, which verifies t 2g and e g states having π and σ characteristics, respectively, following the ligand field theory.…”

“…Figure b refers to a gradual decrease in the XMCD signal with the increasing thickness of the SiO 2 coating due to the nonmagnetic SiO 2 coating at the surface hindering the proper signal of the magnetic core. In the present work, the XMCD measurements were carried out through a bulk-sensitive total fluorescence yield (TFY) mode that has a long probing depth of ∼100 nm , and probe the bulk spin and orbital magnetic moments of NPs at 300 K. The surface-sensitive total electron yield (TEY) mode has a probing depth of ∼10 nm, more active at the surface edge. , This experimental specification in the TFY mode is different from the TEY mode of XMCD as also reported by Amemiya et al − …”

“…To determine the orbital and spin magnetic moments separately with an element-specific probe, XAS and XMCD techniques were employed. Unlike VSM, SQUID, and any other magnetometric measurements, to extract the spin and orbital magnetic moments individually and to learn more about the causes of their electronic and magnetic appearance, element-specific techniques called XAS and XMCD become more helpful. ,,,,− At first, soft X-ray absorption spectroscopy (XAS) was recorded by scanning the energy range across 690 to 735 eV at the Fe L 2,3 edges for all the samples. Figure a shows the normalized XAS spectra (i.e., scriptm + + scriptm − 2 ) of Fe 3 O 4 and SiO 2 @Fe 3 O 4 (S-0 to S-5, as indicated) NCs, where m + refers to the positive and m – to the negative helicities of the polarized light.…”

“…The characteristic peaks around h ν = 709.2 and 720.1 eV, which are involved in absorptions at j = 3 2 (L 3 ) and 1 2 (L 2 ) components gathered from Fe 2p core levels, respectively. The spin ( M spin ) and orbital ( M orb ) magnetic moments are determined from the sum rules − ,− where I L 2 (or I L 3 ) and Δ I L 2 (or Δ I L 3 ) are indicated to be the L 2 (or L 3 ) edge integrated XAS and XMCD intensities as mentioned in Figure e,f. Figure d shows the Fe XMCD spectra of sample S-3 measured at 1 T. Δ m = m + – m – refers to the difference in intensities between the two opposite helicities found from the normalized XAS signals.…”

Local electronic structures of annealing induced phases in cobalt doped TiO2 nanoparticles: a combined study of transmission electron microscopy and x-ray absorption fine structure spectroscopy

“…Carrier-mediated studies in TiO 2 with different phase configurations have been explored theoretically by many researchers [7-9, 12, 13]. Recently, Singh et al and Kumari et al established ferromagnetism in rutile Co-doped TiO 2 and at varying annealing temperatures hence changing the phase with an elaborated discussion through various spectroscopic studies where the ferromagnetism has been found due to equal distribution and proper insertion of Co-ions in TiO 2 matrix [14][15][16]. Most of the previously published works [12][13][14][15][16] were focused on bulk properties either on thin films or NPs using XMCD which is also surface sensitive and shows ferromagnetic behaviour.…”