Novel alkaline earth copper germanates with ferro and antiferromagnetic S=1/2 chains

Journal Article · Fri Feb 15 04:00:00 EST 2013 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/J.JSSC.2012.09.006· OSTI ID:22149995

Brandao, Paula ^[1]; Reis, Mario S. ^[2]; Gai, Zheng ^[3]; Santos, Antonio M. dos, ^[4]

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1. CICECO, Universidade de Aveiro, 3810-193 Aveiro (Portugal)
2. Instituto de Fisica, Universidade Federal Fluminense, Av. Gal. Milton Tavares de Souza s/n, 24210-346 Niteroi-RJ (Brazil)
3. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory Oak Ridge, TN 37831-6487 (United States)
4. 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, Journal Name: Journal of Solid State Chemistry Vol. 198; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ANTIFERROMAGNETISM
CALCIUM COMPOUNDS
COPPER
COPPER OXIDES
GERMANATES
GERMANIUM OXIDES
HYDROTHERMAL SYNTHESIS
INTERACTIONS
LAYERS
MAGNETIC SUSCEPTIBILITY
MONOCLINIC LATTICES
MONOCRYSTALS
ORTHORHOMBIC LATTICES
SPACE GROUPS
WATER
X-RAY DIFFRACTION