Novel alkaline earth copper germanates with ferro and antiferromagnetic S=1/2 chains
- CICECO, Universidade de Aveiro, 3810-193 Aveiro (Portugal)
- Instituto de Fisica, Universidade Federal Fluminense, Av. Gal. Milton Tavares de Souza s/n, 24210-346 Niteroi-RJ (Brazil)
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory Oak Ridge, TN 37831-6487 (United States)
- Quantum Condensed Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory Oak Ridge, TN 37831-6460 (United States)
Two new alkaline earth copper(II) germanates were hydrothermally synthesized: CaCuGeO{sub 4}{center_dot}H{sub 2}O (1) and BaCu{sub 2}Ge{sub 3}O{sub 9}{center_dot}H{sub 2}O (2), and their structures determined by single crystal X-ray diffraction. Compound (1) crystallizes in space group P2{sub 1}/c with a=5.1320(2) Angstrom-Sign , b=16.1637(5) Angstrom-Sign , c=5.4818(2) Angstrom-Sign , {beta}=102.609(2) Degree-Sign , V=443.76(3) Angstrom-Sign {sup 3} and Z=4. This copper germanate contains layers of composition [CuGeO{sub 4}]{sub {infinity}}{sup 2-} comprising CuO{sub 4} square planes and GeO{sub 4} tetrahedra with calcium and water molecules in the inter-layer space. Compound (2) crystallizes in the Cmcm space group with a=5.5593(3) Angstrom-Sign , b=10.8606(9) Angstrom-Sign , c=13.5409(8) Angstrom-Sign , V=817.56(9) Angstrom-Sign {sup 3} and Z=4. This structure contains GeO{sub 6} and CuO{sub 6} octahedra as well as GeO{sub 4} tetrahedra, forming a three-dimensional network of interconnecting six-membered ring channels. The magnetic susceptibility for both samples can be interpreted as S=1/2 chains, in agreement with the copper topology observed in the crystal structure. The susceptibility of (1) exhibits a Bonner-Fisher type behavior, resulting from antiferromagnetic intra-chain interactions without three-dimensional ordering down to 5 K-the lowest measured temperature. This observation, together with the absence of super-exchange paths between the copper chains, make this system particularly promising for the study of low dimensional magnetism. The magnetic properties of (2) show a very weak ferromagnetic near-neighbor interaction along the chain. In this compound a peak the {chi}T plot seems to indicate the onset of interchain antiferromagentic correlations. However, no ordering temperature is detected in the susceptibility data. - Graphical abstract: Copper chains present in CaCuGeO{sub 4}{center_dot}H{sub 2}O and BaCu{sub 2}Ge{sub 3}O{sub 9}{center_dot}H{sub 2}O, two novel copper germanates synthesized hydrothermally, showing antiferromagnetic and ferromagnetic intra-chain interactions respectively. Highlights: Black-Right-Pointing-Pointer The structure of two new chain containing copper germinates is reported. Black-Right-Pointing-Pointer The calcium compound CaCuGeO{sub 4}{center_dot}H{sub 2}O contains corner sharing square planes. Black-Right-Pointing-Pointer The barium compound BaCu{sub 2}Ge{sub 3}O{sub 9}, displays edge sharing octahedra. Black-Right-Pointing-Pointer Susceptibility data show that the Ca compound is a one-dimensional antiferromagnet while Ba is a weak ferromagnet.
- OSTI ID:
- 22149995
- Journal Information:
- Journal of Solid State Chemistry, Vol. 198; Other Information: Copyright (c) 2012 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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