| Research Abstract |
We have focused on a one-dimensional metal-dimer system with dynamical spin-charge-lattice coupling, exhibiting many kinds of charge-ordered states associated with metal-insulator transitions. In this paper, we present on an MMX-chain system in which there exists J-D…-I-M-M-I-… chains. Some of me possible 1-D structural modes for the MMX chain are shown below.
We have focused on a one-dimensional metal-dimer system with dynamical spin-charge-lattice coupling, exhibiting many kinds of charge-ordered states associated with metal-insulator transitions. In this paper, we present on an MMX-chain system in which there exists J-D…-I-M-M-I-… chains. Some of me possible 1-D structural modes for the MMX chain are shown below.
(1) ---M2.5+-M2.5+―X―M2.5+-M2.5+―X―M2.5+-M2.5+―X---
(2) ---M2+-M2―X-M3+-M3+-X―M2+-M2+―X-M3+-M3+-X---
(3) ---M2+-M3+-X―M2+-M3+-X―M2+-M3+-X―M2+-M3+-X---
(4) ---M2+-M3+-X-M3+-M2+―X―M2+-M3+-X-M3+-M2+―X---
According to our recent work, the Ni2(MeCS2)4I salt was found to exhibit a fiel
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d-induced phase transition accompanying a spin transition between a 1-D Heisenberg AF magnetic spin system with J〜-50 K (a-phase) and Curie spin system with J〜0 K (p-phase). In order to investigate two different spin states, several physical measurements were carried out on Ni2(MeCS2)4I.
It exhibits a semiconducting behavior, which is consistent with a Mott-Hubbard insulator. The XPS spectra shows a trapped-valence state of +II and +III. Each phase is considered to have the 1-D structural mode of -I―Ni2+-Ni3+-I-Ni3+-Ni2+―I―Ni2.5+-Ni2.5―I-, which was confirmed by Raman, IR, UV-VIS-NIR spectra and magnetic susceptibility.
At 2 K, if the magnetic field of 5 T is applied, the a-phase is transformed to the p-phase, which can be obtained as a metastable state even at room temperature and zero-field. On the other hand, if the magnetic field of 5 T is applied at 300 K, the P-phase is reversibly transformed to the a-phase. This field-induced phenomenon is considered to be derived from an orbital degree of freedom, resulting the field-induced orbital ordering. Detailed investigations are in progress. Less
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