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August 11
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Aug. 11 - 2a
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9:00 - 9:30
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9:30 - 10:00
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10:00 - 10:30
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| Ion Exchange as a Tool to Explore Two-Dimensional Square Lattice Antiferromagnets |
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Hiroshi Kageyama |
| Soft chemical approach provides us new routes for the construction of new magnetic materials. Two-dimensional (2D) S = 1/2 square-lattice antiferromagnets (CuX)LaB2O7 (X =Cl, Br; B = Nb, Ta) have been obtained by the ion exchange between Dion-Jacobson layered perovskites RbLaB2O7 and CuX2 (see Fig. 1). Here the magnetic [CuX]+ layer is well separated by nonmagnetic perovskite slabs so that 2D magnetic properties are expected. The obtained materials shows a variety of magnetic behaviors. (CuCl)LaNb2O7 has a spin singlet ground state with an energy gap of 2.3 meV to the first excited triplet state [1]. Application of the magnetic field leads to the magnetic order described by the BEC of magnons [2]. On the other hand, (CuBr)LaNb2O7 undergoes a magnetic ordering of the stripe tope at 31 K and the analysis of the data indicates strong frustration in the layer. It is found that (CuCl)LaTa2O7 also exhibits a long-range magnetic ordering at 6 K. We have recently succeeded to obtain the solid solution series (CuClxBr1-x)Nb2O7 (0 < x < 1) and (CuCl)La(Nb1-yTay)O7 (0 < y < 1), which allows to investigate the magnetic phase diagrams between the spin-liquid state and the antiferromagnetic state. The structural and magnetic properties of these systems will be presented.
[1] H. Kageyama et al., J. Phys. Soc. Jpn. 74 (2005) 1702. |