Preparation, Crystal Structure, and Magnetotransport Properties of the New CdCu₃Mn₄O₁₂ Perovskite: A Comparison with Density Functional Theory Calculations

Abstract

The A-site ordered perovskite oxide CdCu 3 Mn 4 O 12 has been synthesized for the first time in polycrystalline form under high pressure (7 GPa) and high temperature (1000 °C) conditions, required to stabilize the small Cd and Cu cations at the A positions of the perovskite. The crystal structure has been studied by X-ray powder diffraction at room temperature. This oxide crystallizes in the cubic space group Im3̅ (no. 204) with the unit-cell parameter a = 7.2179(5) Å at 300 K. The MnO 6 network is extremely tilted, giving rise to a square planar coordination for Cu 2+ cations. The magnetic characterization shows that this compound is ferrimagnetic with an ordering temperature T C = 347 K, well above room temperature. A metallic behavior is displayed between 10 and 300 K. Negative magnetoresistance (MR) of 15% is achieved at 10 K for H = 9 T; MR is still significant at room temperature, displaying values above 7% for H = 9 T. Density functional theory calculations carried out on the density of states lead to electronic and magnetic features in good agreement with the obtained experimental results.

Low-Temperature Structural Modulations in CdMn7O12, CaMn7O12, SrMn7O12, and PbMn7O12 Perovskites Studied by Synchrotron X-ray Powder Diffraction and Mössbauer Spectroscopy

“…The perovskite structure is usually stable at 0.88 < t < 1.09, where t is the Goldschmidt tolerance factor: t = ( r A + r O )/[√2­( r B + r O )], where r A , r B , and r O are the ionic radii of the A, B, and oxygen ions, respectively. There is a special class of perovskite-structure materials with the general formula of (AA′ 3 )­B 4 O 12 that allows the size of A′ and B cations to be very close to each other. − A perovskite-type structure of (AA′ 3 )­B 4 O 12 is stabilized because of a very unusual cation order with 12-fold-coordinated A site and square-coordinated A′ site (actually with four very short A′–O bond lengths, four long A′–O bond lengths, and four very long A′–O bond lengths). Therefore, the A′ site is typically occupied by Jahn–Teller cations, such as Cu 2+ and Mn 3+ , and most of the (AA′ 3 )­B 4 O 12 compounds need high pressure (HP) and high temperature (HT) for their preparation.…”

High-Pressure Synthesis, Crystal Structures, and Properties of CdMn7O12 and SrMn7O12 Perovskites

“…(AA′ 3 )­B 4 O 12 perovskite-structure materials have received a lot of attention because many members of this family show interesting physical and chemical properties, − for example, properties of heavy Fermions, intersite charge transfer and disproportionation, , metal–insulator transitions, giant dielectric constant, collinear and noncollinear magnetic ordering with high magnetic ordering temperatures, and multiferroic properties . (AA′ 3 )­B 4 O 12 perovskites allow large variations in the chemical composition, − for example, with A = Na + , Mn 2+ , Cd 2+ , Ca 2+ , Sr 2+ , R 3+ (R = rare earths), and Bi 3+ ; A′ = Cu 2+ , Mn 3+ , Co 2+ , and Pd 2+ ; and B = Mn 3+/4+ , Fe 3+ , Cr 3+ , Al 3+ , Ti 4+ , V 4+ , Ge 4+ , Sn 4+ , Ru 4+ , Ir 4+ , Ta 5+ , Nb 5+ , Sb 5+ , and others . A very unusual cation order is realized in (AA′ 3 )­B 4 O 12 with 12-fold-coordinated A site and square-coordinated A′ site, the B site has a usual octahedral coordination for perovskites.…”

A remarkable high entropy effect on the magnetic behaviour of quadruple perovskites

“…48 The presence of impurity phases in conventional quadruple perovskites even when synthesized under high pressure is reported by several authors. 46,[48][49][50][51][52][53][54][55][56][57] About 9% Mn 2 O 3 , Mn 3 O 4 and CaMn 2 O 4 are reported in CaMn 7 O 12 . 49 The phase purity of BiCu 3 Mn 4 O 12 synthesized under a pressure of 6 GPa is only B87% along with Bi 2 (CO 3 )O 2 and CuO impurities.…”