Joke Hadermann

Publications (147) View all

• Article: Structural and Magnetic Phase Transitions in the A(n)B(n)O(3n-2) Anion-Deficient Perovskites Pb(2)Ba(2)BiFe(5)O(13) and Pb(1.5)Ba(2.5)Bi(2)Fe(6)O(16).

  A M Abakumov, M Batuk, A A Tsirlin, O A Tyablikov, D V Sheptyakov, D S Filimonov, K V Pokholok, V S Zhidal, M G Rozova, E V Antipov, J Hadermann, G Van Tendeloo
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  ABSTRACT: Novel anion-deficient perovskite-based ferrites Pb(2)Ba(2)BiFe(5)O(13) and Pb(1.5)Ba(2.5)Bi(2)Fe(6)O(16) were synthesized by solid-state reaction in air. Pb(2)Ba(2)BiFe(5)O(13) and Pb(1.5)Ba(2.5)Bi(2)Fe(6)O(16) belong to the perovskite-based A(n)B(n)O(3n-2) homologous series with n = 5 and 6, respectively, with a unit cell related to the perovskite subcell a(p) as a(p)√2 × a(p) × na(p)√2. Their structures are derived from the perovskite one by slicing it with 1/2[110](p)(1̅01)(p) crystallographic shear (CS) planes. The CS operation results in (1̅01)(p)-shaped perovskite blocks with a thickness of (n - 2) FeO(6) octahedra connected to each other through double chains of edge-sharing FeO(5) distorted tetragonal pyramids which can adopt two distinct mirror-related configurations. Ordering of chains with a different configuration provides an extra level of structure complexity. Above T ≈ 750 K for Pb(2)Ba(2)BiFe(5)O(13) and T ≈ 400 K for Pb(1.5)Ba(2.5)Bi(2)Fe(6)O(16) the chains have a disordered arrangement. On cooling, a second-order structural phase transition to the ordered state occurs in both compounds. Symmetry changes upon phase transition are analyzed using a combination of superspace crystallography and group theory approach. Correlations between the chain ordering pattern and octahedral tilting in the perovskite blocks are discussed. Pb(2)Ba(2)BiFe(5)O(13) and Pb(1.5)Ba(2.5)Bi(2)Fe(6)O(16) undergo a transition into an antiferromagnetically (AFM) ordered state, which is characterized by a G-type AFM ordering of the Fe magnetic moments within the perovskite blocks. The AFM perovskite blocks are stacked along the CS planes producing alternating FM and AFM-aligned Fe-Fe pairs. In spite of the apparent frustration of the magnetic coupling between the perovskite blocks, all n = 4, 5, 6 A(n)Fe(n)O(3n-2) (A = Pb, Bi, Ba) feature robust antiferromagnetism with similar Néel temperatures of 623-632 K.
  Inorganic Chemistry 02/2013; · 4.60 Impact Factor
• Article: Synthesis and properties of the theoretically predicted mixed-valent perovskite superconductors: CsTlX3 (X = F, Cl)

  M. Retuerto, T. Emge, M. R. Li, Z. P. Yin, M. Croft, A. Ignatov, P. W. Stephens, J. Hadermann, J. W. Simonson, M. C. Aronson, A. Pan, D. N. Basov, G. Kotliar, M. Greenblatt
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  ABSTRACT: Recently CsTlCl3 and CsTlF3 perovskites were predicted theoretically to be potential superconductors. The synthesis of these two new compounds, together with complete characterizations of the samples is reported for the first time. CsTlCl3 is obtained as orange single crystals and CsTlF3 as light brown powders. The structure of the samples was determined by electron diffraction, synchrotron powder x-ray diffraction and single crystal x-ray diffraction. CsTlCl3 is obtained in two different polymorphs: a tetragonal phase (space group I4/m), similar to CsAuCl3, with Tl1+ and Tl3+ in two different crystallographic positions, and therefore with charge ordering; CsTlCl3 was also obtained as a cubic and less distorted phase (space group Fm-3m), also with two different positions for Tl1+ and Tl3+. CsTlF3 was obtained as a cubic phase with space group Fm-3m and Tl1+ and Tl3+ in two unique sites. All three compounds are paramagnetic; according to theory, hole doping and high pressure are required to achieve superconductivity in the CsTlX3 (X = F, Cl) cubic perovskites. The mixed Tl1+ and Tl3+ valence has been confirmed by x-ray absorption spectroscopy. The optical gap has been determined by spectroscopic techniques to be ~2.5 eV, in reasonable agreement with that calculated by first-principles density functional theory (~2.1 eV). The theoretical design and the experimental validation of CsTlF3 and CsTlCl3 cubic perovskites is an extraordinary starting point since, in theory, superconductivity in these materials can be achieved in cubic phases.
  02/2013;
• Source

  Available from: Joke Hadermann

  Dataset: 2012 GB SrFeMoO

  M Retuerto, M-R Li, Y B Go, A Ignatov, M Croft, K V Ramanujachary, J Hadermann, J P Hodges, R H Herber, I Nowik, M Greenblatt
• Source

  Available from: Manrong Li

  Dataset: IC-Magnetic and Structural Studies of the Multifunctional Material SrFe0.75Mo0.25O3

  M Retuerto, M-R Li, Y B Go, A Ignatov, M Croft, K V Ramanujachary, J Hadermann, J P Hodges, R H Herber, I Nowik, M Greenblatt
• Source

  Available from: Manrong Li

  Dataset: IC-Magnetic and Structural Studies of the Multifunctional Material SrFe0.75Mo0.25O3−δ

  M Retuerto, M-R Li, Y B Go, A Ignatov, M Croft, K V Ramanujachary, J Hadermann, J P Hodges, R H Herber, I Nowik, M Greenblatt