Pulsed-ESR Study of Spin Solitons as a Probe of Neutral-to-Ionic Phase Transition of TTF-CA Single Crystal

Ionic phase of charge-transfer crystal composed of tetrathiafulvalene (TTF) and p -chloranil (CA) has been studied by two-pulse electron-spin echo (ESE) at 4 K. By measuring the angular dependence of the field-swept ESE spectrum, at least three kinds of paramagnetic centers have been resolved, which are presumably ascribed to spin solitons formed at domain boundary. With varying the time separation between the microwave pulses, envelope modulations due to anisotropic hyperfine interaction have been detected. By analyzing the modulation, we have firstly obtained ENDOR spectrum of the spin solitons. Response of the ESE intensity for the optical excitation has been also examined.