Optical absorption zeeman spectroscopy of rare earth orthochromites

The optical absorption spectrum of Ho in HoCrO₃ in the phase Γ ₂ (Cr: G _z F _x ; Ho: f _x c _y ) and Γ {₄/^'} (Cr: G _x F _z ; Ho: f _y c _x ) and the magnetization and the susceptibility of HoCrO₃ have been studied as a function of temperature and applied magnetic field. The experimental data for the Ho ground state splitting are analyzed using a molecular field approach. The analysis shows that the Cr — Ho interaction is predominantly antisymmetric exchange. The Ho — Ho interaction is of exchange as well as of dipolar origin. The phase diagram for the configurations Γ ₂ and Γ {₄/^'} in the H — T plane for fields H ∥ y is determined in the temperature region 1.8 K≦ T≦15 K.