In order to investigate the electronic state in the normal state of high- Tc cuprates in a wide range of temperature and hole concentration, specific-heat, electrical-resistivity, magnetization, and muon-spin-relaxation measurements have been performed in nonsuperconducting Ni-substituted La 2-xSrxCu1-yNiyO4 where the superconductivity is suppressed through the partial substitution of Ni for Cu without disturbing the Cu-spin correlation in the CuO2 plane so much. In the underdoped regime, it has been found that there exist both weakly localized holes around Ni and itinerant holes at high temperatures. With decreasing temperature, all holes tend to be localized, followed by the occurrence of variable-range hopping conduction at low temperatures. Finally, in the ground state, it has been found that each Ni2+ ion traps a hole strongly and that a magnetically ordered state appears. In the overdoped regime, on the other hand, it has been found that a Kondo-type state is formed around each Ni2+ spin at low temperatures. In conclusion, the ground state of nonsuperconducting La2-xSrxCu1-yNi yO4 changes upon hole doping from a magnetically ordered state with the strong hole trapping by Ni2+ to a metallic state with Kondo-type behavior due to Ni2+ spins, and the quantum phase transition is crossoverlike due to the phase separation into short-range magnetically ordered and metallic regions.
|ジャーナル||Physical Review B - Condensed Matter and Materials Physics|
|出版ステータス||Published - 2010 8 23|
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