Temperature- and Pressure-Induced Spin Crossover in Co1+xCr2-xSe4 (x = 0.24): A Diffraction Study

Area of Science:

• Solid-state chemistry
• Materials science
• Magnetism

Background:

• The Co1+xCr2-xSe4 phase exhibits complex magnetic and structural properties.
• Spin-crossover (SCO) phenomena in transition metal compounds are of significant interest for materials applications.

Purpose of the Study:

• To investigate the high- to low-spin-state transition of Co(2+) ions in the Co1+xCr2-xSe4 phase.
• To explore the influence of temperature and pressure on the spin-state transition and structural behavior.
• To understand the coupling between spin-conversion and physical properties for potential material tuning.

Main Methods:

• Temperature-dependent single-crystal synchrotron radiation diffraction experiments.
• Pressure-dependent single-crystal synchrotron radiation diffraction experiments.
• Analysis of previously reported physical property studies.

Main Results:

• A high- to low-spin-state transition for Co(2+) ions was observed around 230 K with a 75 K spin-crossover (SCO) region.
• A similar Co(2+) spin-state transition was observed at 14.5 GPa with a 5 GPa SCO region.
• The structural behavior under pressure differs from that observed with temperature changes.

Conclusions:

• The Co1+xCr2-xSe4 phase exhibits temperature- and pressure-induced spin-state transitions.
• The spin-conversion process is coupled with physical property changes, allowing for controlled tuning.
• Compositional and structural modifications can be used to tailor the material's physical response.