title: Local atomic structure and magnetic ordering of iron in Fe-chitosan complexes.
abstract: The iron crosslinked chitosan (Ch-Fe-CL) and N-carboxylmethyl chitosan (N-CM-Ch-Fe) complexes were studied by complementary techniques: structurally sensitive Mössbauer and X-ray absorption methods, as well as static magnetic measurements. A detailed and consistent description of these complexes including, besides the overall magnetic behavior, the spin ordering and local atomic structure around Fe ions is presented. Fe atoms in the investigated samples are mostly penta-coordinated and appear in a high spin Fe (3+) ionic state. In Ch-Fe-CL, two kinds of Fe near neighbors are equally probable and several Fe atoms are situated in the second coordination sphere. The magnetic interactions between these Fe ions lead to a sperimagnetic-like ordering. In N-CM-Ch-Fe, only one Fe neighborhood was found. Other Fe atoms were identified neither in the first nor in the second coordination sphere, but the third coordination sphere indicates the presence of Fe atoms. The magnetic coupling between these atoms is antiferromagnetic, but the dominant part of Fe in this sample remains in a paramagnetic state.
authors.affiliation: Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46 PL-02668, Warsaw, Poland. mklepka@ifpan.edu.pl
authors.forename: Marcin T
authors.initials: MT
authors.lastname: Klepka
authors.forename: Nataliya
authors.initials: N
authors.lastname: Nedelko
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Greneche
authors.forename: Krystyna
authors.initials: K
authors.lastname: Lawniczak-Jablonska
authors.forename: Iraida N
authors.initials: IN
authors.lastname: Demchenko
authors.forename: Anna
authors.initials: A
authors.lastname: Slawska-Waniewska
authors.forename: Clovis A
authors.initials: CA
authors.lastname: Rodrigues
authors.forename: Aline
authors.initials: A
authors.lastname: Debrassi
authors.forename: Cristiani
authors.initials: C
authors.lastname: Bordini
mesh_terms: D048271:Chitosan / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D008280:Magnetics; D015394:Molecular Structure; D015204:Spectroscopy, Mossbauer; D013057:Spectrum Analysis; D014965:X-Rays
chemical_list: D005290:Ferric Compounds; C068302:N-(carboxymethyl)chitosan; D048271:Chitosan; D007501:Iron