Spin-State Switching of Spin-Crossover Complexes on Cu(111) Evidenced by Spin-Flip Spectroscopy

Area of Science:

• Materials Science
• Molecular Electronics
• Surface Science

Background:

• Spin-crossover (SCO) compounds exhibit bistability, switching between low-spin (LS) and high-spin (HS) states with distinct properties.
• Controlling and identifying these spin states at the single-molecule level is crucial for molecular device applications but remains challenging.

Purpose of the Study:

• To investigate the spin-crossover complex [Fe(HB(1,2,4-triazol-1-yl)3)2] on a Cu(111) surface.
• To achieve direct identification of molecular spin states in single SCO molecules using advanced experimental techniques.

Main Methods:

• Utilized scanning tunneling microscopy (STM) to probe single molecules on a Cu(111) surface.
• Employed density functional theory (DFT) calculations to support experimental findings.
• Achieved spin crossover via electron injection and resolved spin-flip excitations in scanning tunneling spectra under a magnetic field.

Main Results:

• Demonstrated spin crossover in single SCO molecules within dense islands through controlled electron injection.
• Successfully identified the molecular spin state by resolving spin-flip excitations in STM spectra under an applied magnetic field.
• Revealed the presence of magnetic anisotropy in the high-spin (HS) state of the SCO molecules.

Conclusions:

• Direct identification of molecular spin states in SCO compounds is feasible using STM and magnetic fields.
• The study provides a pathway for probing and controlling spin states at the single-molecule level for future molecular spintronic devices.