New Electronic Excitation at the Boundary of Ferromagnetic and Antiferromagnetic Phases in the One-Dimensional Ising Antiferromagnet CsFeCl₃.2H₂O

Magnetoabsorption spectra and magnetization processes were investigated in a quasi-one-dimensional Ising-like antiferromagnet CsFeCl₃.2H₂O using steady high magnetic fields of up to 27 T. Besides the Zeeman splitting of an exciton line, an extra absorption line was found in the field range of 12 T-16 T, where the magnetic phase transition from antiferromagnetic to forced ferromagnetic phase took place. The extra line was concluded to be due to an electronic excitation at the boundary between ferromagnetic and antiferromagnetic phases in the linear chain.