Magnetic field-induced spin-crossover transition in [MnIII(taa)] studied by x-ray absorption spectroscopy

X-ray absorption near-edge structure (XANES) spectra of Mn in a spin-crossover compound, [MnIII(taa)], was studied in pulsed high magnetic fields up to 37 T. The significant changes in the XANES spectra, related to the spin-crossover from the low-spin (LS) state to high-spin (HS) state, were found to be induced by magnetic fields at temperatures down to 17 K. The fraction of the field-induced HS states was, at most, 30%, and the magnetic field dependence of the HS fraction exhibited hysteresis. The observed field-induced spin-crossover at T = 17 K (T/Tc ∼ 0.4, where Tc (= 46 K) is the spin-crossover transition temperature) cannot be understood as the field-induced macroscopic phase transition, because the transition magnetic field is known to be higher than 55 T at low temperatures. The observed field-induced LS-HS transition is likely the local microscopic transition at the single-molecule level.