A New State Realized by Mixing of Ni and Pd as the Metal Ions in MX-Chains : Effects of Electron Correlation and Interpretation of Raman Data

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It has been argued theoretically that a new state, namely, no halogen displacements around Pd ions and, consequently, their trivalent states with finite magnitudes of spin, will be realized by at least 50%inclusion of Ni ions in Pd-Ni mixed-metal MX-chains. This state is peculiar to such mixed-metal systems, because it is never found as a ground state for homo-metal chains of Pd. Moreover, from the theoretical viewpoint, strong electron-lattice interaction and strong electron-electron Coulombic repulsion are mixed up to give a very interesting example for the study of both. Here we go beyond the previous theoretical work that was based on a Hartree-Fock (HF) calculation and investigate the same system by a quantum Monte-Carlo method applied to a Peierls-Hubbard model. The obtained result is qualitatively the same as the previous one and therefore reinforces the above interpretation with a preliminary result for magnetic -susceptibility. Moreover, we show statistically averaged lattice states for rather continuous composition changes, within the framework of HF calculations. The obtained result. explains well the Raman data.
社団法人日本物理学会の論文
2002-01-15