On the magnetic structure of DyNiO{sub 3}

• Published in: Journal of solid state chemistry 2009-07, Vol.182 (7)
• Main Authors: Munoz, A., Alonso, J.A., Martinez-Lope, M.J., Fernandez-Diaz, M.T.
• Format: Article
• Language: English
• Subjects: ANTIFERROMAGNETISM; ATOMIC FORCE MICROSCOPY; CHALCOGENIDES; CHARGED PARTICLES; COHERENT SCATTERING; CRYSTAL LATTICES; CRYSTAL STRUCTURE; CRYSTALLOGRAPHY; DIFFRACTION; DYSPROSIUM COMPOUNDS; DYSPROSIUM IONS; IONS; MAGNETIC MOMENTS; MAGNETISM; MAGNETIZATION; MATERIALS SCIENCE; MICROSCOPY; MINERALS; MONOCLINIC LATTICES; NEUTRON DIFFRACTION; NICKEL COMPOUNDS; NICKEL IONS; OXIDE MINERALS; OXIDES; OXYGEN COMPOUNDS; PEROVSKITE; PEROVSKITES; PHYSICAL PROPERTIES; RARE EARTH COMPOUNDS; SCATTERING; SPACE GROUPS; SYMMETRY GROUPS; TEMPERATURE RANGE; TEMPERATURE RANGE 0000-0013 K; TEMPERATURE RANGE 0065-0273 K; TEMPERATURE RANGE 0273-0400 K; TEMPERATURE RANGE 0400-1000 K; THERMODYNAMIC PROPERTIES; TRANSITION ELEMENT COMPOUNDS; TRANSITION TEMPERATURE; VALENCE
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2009.05.013

The crystallographic structure of DyNiO{sub 3} has been investigated at T=200, 100, and 2 K from high-resolution neutron powder diffraction (NPD) data. We show that the structure is monoclinic, space group P2{sub 1}/n, from the metal-insulator transition temperature at T{sub MI}=564 K down to 2 K. The Ni atoms occupy two different sites 2d (Ni1) and 2c (Ni2), whose valences, estimated from bond-valence consideration, are +2.43(1) and +3.44(1) at 2 K, respectively. This is interpreted as the result of a partial charge disproportionation of the type 2Ni{sup 3+}->Ni1{sup (3-{delta})+}+Ni2{sup (3+{delta})+}, with {delta}{approx}0.55 at T=2 K. The magnetic structure has been studied from a NPD pattern at T=2 K, well below the establishment of the antiferromagnetic (AFM) ordering at T{sub N}=154 K, as well as from sequential data collected from 16 K down to 2 K. The magnetic order is defined by the propagation vector k=(1/2,0,1/2). Two possible magnetic structures are compatible with the magnetic intensities. In the second solution both Ni sublattices participate in the magnetic order, as well as Dy since it corresponds to a total disproportionation of Ni{sup 3+} to Ni{sup 2+} and Ni{sup 4+}. In the second solution both Ni sublattices participate in the magnetic order, as well as Dy. The magnetic moments for Ni1 and Ni2 atoms at T=2 K are 1.8 (2) and 0.8 (2) mu{sub B}, respectively. These values are also compatible with a partial charge disproportionation. Dy{sup 3+} ions exhibit long-range magnetic ordering below 8 K. An abrupt contraction of the unit-cell volume is observed at this temperature, due to a magnetoelastic coupling. The magnetic moment for Dy{sup 3+} at T=2 K is 7.87 (6) {mu}{sub B}. - Abstract: DyNiO{sub 3} undergoes a metal-insulator transition at T{sub MI}=564 K. Below T{sub MI} the structure is monoclinic with two different sites for the Ni atoms, which present a different valence. It is interpreted as a partial charge disproportionation. Below T{sub N}=154 K DyNiO{sub 3} orders with an antiferromagnetic structure defined by k=(1/2,0,1/2). Display Omitted