| Budget Amount *help |
¥16,700,000 (Direct Cost: ¥16,700,000)
Fiscal Year 2000: ¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 1999: ¥13,800,000 (Direct Cost: ¥13,800,000)
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| Research Abstract |
In this study, we have precisely investigated which metal-elements can be put into the A', A and B sites in the A'_3ABO_6 compounds with K_4CdCl_6-type structure in order to clarify the general stability condition of this structure. Thus, the purpose of the study is to search the new various 1D-magnets with this structure by utilizing the obtained conditions and to investigate their physical properties. Experimental results are as follows.
Searching the new compounds with the K_4CdCl_6-type structure, we have been succeeded in synthesizing these three new compounds : Ca_3CoIrO_6, Ca_3CoRuO_6 and Ca_3CoRhO_6. Especially, Ca_3CoRhO_6 indicates the behaviors of the 2D-triangular lattice antiferromagnets (2D-TLA) with the Ising-type ferromagnetic spin chains just as the case with Ca_3Co_2O_6, both of which indicate two Neel temperature, T_<N1> and T_<N2>. In the temperature regime between T_<N1> and T_<N2>, the magnetic state of Ca_3CoRhO_6 has been found to be the partially disordered antiferromagnetic (PDA) one, which is characteristic to the case of the 2D-TLA, investigated by neutron diffraction experiments. This is the first observation of the PDA state in the 2D-TLA with Ising-type ferromagnetic chains, although the PDA state has been hardly thought to be realized in the 2D-TLA case with the ferromagnetic chains. Furthermore, the PD spin chains have been found to be frozen randomly below T_N, because the ferromagnetic hatchings can hardly flip up to down and down to up. Consequently, the transition at T_N is that from the PDA state to the spin glass state with decreasing temperature, below which the coexistence state is realized of 2/3 antiferromagnetic chains and 1/3 frozen spin chains. In order to break the frozen state and to flip the spin chain, we found to need very high magnetic fields more than several 10 T at least. Further investigations are necessary for fully understanding of the low dimensional magnetic systems.
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