Anomalous behavior of magnetic linear dichroism in HoFe3(BO3)4 crystal with spiral magnetic ordering

Abstract

Spectra of magnetic linear dichroism of the optical transition 5I8 → 5F3 were studied in the HoFe3(BO3)4 single crystal as a function of magnetic field directed along the trigonal c axis at the temperature 2 K. It has been found that dichroism in the basal plane appears even in low magnetic field in the easy-axis state of the crystal. This indicates a violation of the axial symmetry of spiral structure of Ho magnetic moments. Moreover, the sign of dichroism is changed with the change of the magnetic field sign both below and above the field of spin-reorientation transition. This could mean that the average magnetic moment of three Ho3+ ions forming the spiral rotates in magnetic field both relative to the c axis and in the ab plane.