Production of spin polarized 12N through heavy ion reactions

The structural and magnetic properties of Ho substituted BiFeO₃ (BHFO) have been investigated using ⁵⁷Fe Mössbauer spectroscopy and X-Ray diffraction (XRD) as a function of temperature. The Mössbauer spectrum obtained at room temperature for the as-synthesized BHFO sample exhibits broadened features due to the hyperfine field distributions related to the local variation of the neighbourhood of Fe and the magnetic hyperfine splitting patterns are indicative of magnetic ordering, mostly probably screwed or slightly antiferromagnetic. The spectrum was fitted with two superimposed asymmetric sextets, with similar hyperfine magnetic fields of B_hf1 = 48.0(1) T and B_hf2 = 49.0(1) T, corresponding to rhombohedral BFO. The hyperfine fields of the magnetic components decreased systematically with increasing temperature to a ‘field distribution’ just below the Néel temperature, T_N ~ 600 K. At temperatures above 600 K, the spectral line associated with the Bi₂₅FeO₄₀ impurity phase dominates the spectra. This phase is confirmed by XRD measurements. From the temperature dependence of the site populations of the spectral components an average Debye temperature of θ _D = 240(80) K has been estimated.