Enhanced ferromagnetic moment in Co-doped BiFeO3 thin films studied by soft x-ray circular dichroism

Abstract

BiFeO3 (BFO) shows both ferroelectricity and magnetic ordering at room temperature but its ferromagnetic component, which is due to spin canting, is negligible. Substitution of transitionmetal atoms such as Co for Fe is known to enhance the ferromagnetic component in BFO. In order to reveal the origin of such magnetization enhancement, we performed soft x-ray absorption spectroscopy (XAS) and soft x-ray magnetic circular dichroism (XMCD) studies of BiFe1−xCoxO3 (x = 0 to 0.30) (BFCO) thin films grown on LaAlO3(001) substrates. The XAS results indicated that the Fe and Co ions are in the Fe 3+ and Co 3+ states. The XMCD results showed that the Fe ions show ferromagnetism while the Co ions are antiferromagnetic at room temperature. The XAS and XMCD measurements also revealed that part of the Fe 3+ ions are tetrahedrally co-ordinated by oxygen ions but that the XMCD signals of the octahedrally coordinated Fe 3+ ions increase with Co content. The results suggest that an impurity phase such as the ferrimagnetic γ-Fe2O3 which exists at low Co concentration decreases with increasing Co concentration and that the ferromagnetic component of the Fe 3+ ion in the octrahedral crystal fields increases with Co concentration, probably reflecting the increased canting of the Fe 3+ ions.

Orbital magnetic moment and coercivity ofSiO2-coated FePt nanoparticles studied by x-ray magnetic circular dichroism

“…In Fig. 2(a) one can see that after having subtracted the FePt XAS spectrum multiplied by ∼0.5, the spectral line shape became similar to that of BiFeO 3 , where the Fe 3+ ion is located at the O h site [23], shown in the bottom of Fig. 2(a).…”

“…[8], dotted curve) are shown at the top. The XMCD spectrum of BiFeO 3 by Singh et al [23] is shown at the bottom.…”

“…Spectra after subtraction of the FePt ones from the measured ones by different ratios are indicated below by dot-dashed curves. The XAS spectrum of BiFeO 3 by Singh et al [23] is shown at the bottom. (b) The experimental XMCD spectrum (crosses) and the FePt one (Ref.…”

Electronic and magnetic properties of off-stoichiometric Co2MnβSi/MgO interfaces studied by x-ray magnetic circular dichroism

“…By applying the sum rules [1,2,20,[25][26][27][28][29][30][31], we obtained the spin and orbital magnetic moments of the Mn atom from the XAS and XMCD spectra. We assumed the contribution of the dipole operator term T z in the spin sum rule to be negligibly small because the Mn atom in CMS is located at the high-symmetry T d site [2].…”

“…To determine the Co magnetic moment, we applied the sum rules [1,2,20,[25][26][27][28][29][30][31] as in the case of the Mn L 3,2 -edges. Since the Co atoms are also in the highlysymmetry T d crystal field, we again neglect the T z term in the spin sum rule [2].…”