Fig. 2
From: Expansion of the spin cycloid in multiferroic BiFeO3 thin films
Expansion of the spin cycloid with film thickness. Neutron diffraction reciprocal space maps of the a 65 nm, d 90 nm, and e 142 nm Co-doped BFO films. The double peak structure indicative of a cycloidal modulation, with propagation direction of \([11\bar 2]\), is present around the \((\frac{1}{2}\frac{1}{2}\frac{1}{2})\) position for all films. Results of the simulation of the neutron diffraction measurements of the 65 nm film based on the domain structure from XRD data are shown for a cycloid period of b 64 nm and c 84 nm. Note that the multiple ferroelastic domains in the 65 nm a and 90 nm d films obscure the splitting. The length of the spin cycloid as extracted from line profiles along \([11\bar 2]\) is 67.8(4.8) nm and 69.7(5.3) nm for these films, respectively. e RSM maps of the 142 nm single domain BFO film. The analysis did provide a cycloidal length of 64.4(2.8) nm. f Thickness dependence of the cycloid period. The open circle corresponds to an un-doped BFO film with a cycloidal length of 64.7(10) nm (from ref. 10) The cycloidal length of bulk BFO of 64 nm is indicated as horizontal line.14,15,16,18 The error bars correspond to 1 s.d. of Gaussian fits to the diffraction peaks. The inset shows the experimental scattering geometry of a (110)-oriented thin film with two ferroelastic domains with ferroelectric polarization vectors P1 and P2
