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Title: Enhancement of magnetoresistance and ferromagnetic coupling in the complex perovskites CaCu{sub 3}(Mn{sub 4−x}Al{sub x})O{sub 12} (x = 0, 0.2, 0.4, and 0.6): A neutron diffraction study

New compounds of the series CaCu{sub 3}(Mn{sub 4−x}Al{sub x})O{sub 12} have been prepared under high pressure conditions (2 GPa), in the presence of KClO{sub 4} as oxidizing agent to stabilize Mn{sup 3+,4+} mixed valence. The polycrystalline samples have been characterized by x-ray diffraction, neutron powder diffraction (NPD), magnetic, and magnetotransport measurements. All the samples are cubic, space group Im-3. These oxides adopt a superstructure of ABO{sub 3} perovskite given by the long-range 1:3 ordering of Ca{sup 2+} and Cu{sup 2+} ions at the A sublattice. The NPD study for x = 0.4 shows that Al{sup 3+} ions are statistically distributed at the octahedral positions, being the (Mn,Al)O{sub 6} octahedra strongly tilted, with superexchange (Mn,Al)-O-(Mn,Al) angles of 142.1°. Also, neutron data clearly show that some Mn{sup 3+} ions (0.65(2) per formula) are located together with Cu{sup 2+} at the square-planar 6b positions. Regarding the magnetic properties, all the compounds present a spontaneous increase of the magnetization below T{sub C}, typical of ferro-or ferrimagnetic materials, with T{sub C} decreasing upon Al introduction. The magnetic structure determined from low-temperature NPD data unveils a ferromagnetic coupling between (Cu{sup 2+}, Mn{sup 3+}){sub 6b} spins and Mn{sub 8c} spins at octahedral positions; this is in contrastmore » with the ferrimagnetic structure observed for RCu{sub 3}Mn{sub 4}O{sub 12} and CaCu{sub 3}Mn{sub 4}O{sub 12}, where an AFM coupling is observed between both magnetic sublattices. Interestingly, an enhancement of the magnetoresistance effect is observed for x = 0.2, well beyond that found for the parent compound. This effect, in materials subtly doped with non-magnetic elements at the Mn positions, may be of interest for applications.« less
Authors:
;  [1] ;  [2] ; ;  [3] ;  [4] ;  [5]
  1. Faculty of Sciences, Sfax University, Sfax, B.P. 1171-3000 (Tunisia)
  2. Departamento de Química Física I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, E-28040 Madrid (Spain)
  3. Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, E-28049 Madrid (Spain)
  4. Institut Laue-Langevin, B.P. 156, F-38042 Grenoble Cedex 9 (France)
  5. National School of Engineers, Sfax University, Sfax, B.P. W 3038 (Tunisia)
Publication Date:
OSTI Identifier:
22489457
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 118; Journal Issue: 10; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ALUMINIUM IONS; ATOMIC FORCE MICROSCOPY; CALCIUM IONS; COPPER IONS; DOPED MATERIALS; FERRIMAGNETIC MATERIALS; MAGNETIC PROPERTIES; MAGNETIZATION; MAGNETORESISTANCE; MANGANESE IONS; NEUTRON DIFFRACTION; OXIDES; PEROVSKITE; POLYCRYSTALS; POTASSIUM PERCHLORATES; PRESSURE RANGE GIGA PA; SPACE GROUPS; SPIN; X-RAY DIFFRACTION