Synthesis and Characterization of Sr2Cu(W1鈥?i>xMox)O6: A Quasi-Two-Dimensional Magnetic System

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• 作者：S. Vasala ; J.-G. Cheng ; H. Yamauchi ; J. B. Goodenough ; M. Karppinen
• 刊名：Chemistry of Materials
• 出版年：2012
• 出版时间：July 24, 2012
• 年：2012
• 卷：24
• 期：14
• 页码：2764-2774
• 全文大小：459K
• 年卷期：v.24,no.14(July 24, 2012)
• ISSN：1520-5002

文摘

Here, we report the synthesis of the double-perovskite system Sr₂Cu(W_1鈥?i>xMo_x)O₆, with x = 0.0鈥?.0, where the Mo-containing members have not been synthesized before. This system provides an example of a quasi-two-dimensional S = ¹/₂ square lattice, with the possibility of magnetic frustration. The compounds were synthesized under ambient pressure for 0 鈮?x 鈮?0.6 and under high pressure (HP) for 0.7 鈮?x 鈮?1.0. A small percentage of impurities, primarily Sr(W,Mo)O₄, was present in all samples and increased for x 鈮?0.5. Tetragonal distortion of the compounds decreases with increasing x, and correspondingly, a first-order tetragonal-cubic cooperative Jahn鈥揟eller ordering of the 3d hole on the Cu^II into d_x²鈥搚² orbitals below a T_JT 鈮?920 掳C in Sr₂CuWO₆ is lowered to a T_JT 鈮?500 掳C in Sr₂CuMoO₆. The samples were all insulators, but the band gap was found to decrease with increasing Mo content due to the weaker Mo 4d鈥揙 2p hybridization compared to that of W 5d鈥揙 2p. Ordering of the Cu^II holes into d_x²鈥搚² orbitals creates magnetic interactions between spins S = ¹/₂ with antiferromagnetic 180掳 Cu鈥揙鈥?W,Mo)鈥揙鈥揅u parameters (鈭?i>J₂) and ferromagnetic 90掳 Cu鈥揙鈥?W,Mo)鈥揙鈥揅u parameters (+J₁) in the (001) planes. Magnetic susceptibility showed no long-range magnetic order in any sample down to 5 K.

Keywords:

kite+oxide&qsSearchArea=searchText">double-perovskite oxide; high-pressure synthesis; Jahn鈭扵eller distortion; electronic band structure calculation; mensional+magnetism&qsSearchArea=searchText">low-dimensional magnetism