Pressure- and temperature-induced spin-state transition in single-crystalline La_(1-x)Sr_xCoO_3 (x = 0.10 and 0.33)

摘要

We report on the temperature dependence of magnetization (M) and resistivity (ρ) of La_(1-x)Sr_xCoO_3 (x=0.10 and 0.33) single crystals. For x=0.10, the temperature dependence of field-cooled magnetization (M_(FC)) and zero-field-cooled magnetization (M_(ZFC)) are similar to that expected for a canonical spin-glass system. The thermal response of M_(ZFC) for x=0.33 indicates a glassy ferromagnetic state. We observe that the ferromagnetic transition temperature T_C decreases and p increases rapidly with increasing pressure (P) for the metallic sample (x=0.33) while the dependence of p on P for the insulating sample (x=0.10) is quite complicated; the pressure coefficient of resistivity (dρ/dT) is sensitive to temperature and applied pressure due to the strong interplay between the pressure-induced band broadening and spin-state transition phenomenon. dp/dT is large and negative at low-pressure and low-temperature regimes while small and positive at high pressures (P>5.4 GPa) and high temperatures (T> 110 K).