High-Resolution Spectroscopy of Low-Temperature Phase Transitions in Copper Metaborate CuB2O4

The linear magnetic dichroism in the crystallographically isotropic ab plane of a tetragonal CuB2O4 single crystal has been investigated by high-resolution Fourier spectroscopy at temperatures of 1.4–22 K. Magnetic phase transitions are found at T < 2.0 K and their nature is discussed.