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

Journal Article · Mon Sep 14 00:00:00 EDT 2015 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4930175· OSTI ID:22489457

Ben Hassine, R.; Cherif, W. ^[1]; Sánchez-Benítez, J. ^[2]; Mompean, F. J.; Fernández-Díaz, M. T. ^[3]; Elhalouani, F. ^[4]

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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. Institut Laue-Langevin, B.P. 156, F-38042 Grenoble Cedex 9 (France)
4. National School of Engineers, Sfax University, Sfax, B.P. W 3038 (Tunisia)

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 contrast 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.

• OSTI ID: 22489457
• Journal Information: Journal of Applied Physics, Vol. 118, Issue 10; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

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