Weak ferromagnetism in copper metaborate CuB2O4

CuB2O4 single crystals have been grown and their magnetic and resonance pro perties have been investigated for the first time. The temperature dependen ce of the susceptibility was found to contain features at T = 21 and 10 K. The CuB2O4 single crystal transformed at T = 21 K to a weakly ferromagnetic state. The sharp drop in susceptibility at T < 10 K is caused by a transit ion of the magnetic system of CuB2O4 to an antiferromagnetic state. The eff ective magnetic moment of the Cu2+ ion, determined from the high-temperatur e part of the magnetic susceptibility, is 1.77 mu(B). The room-temperature g factors are, respectively, 2.170 and 2.133 for magnetic field parallel an d perpendicular to the c axis of the crystal. The antiferromagnetic resonan ce parameters in the weakly ferromagnetic and antiferromagnetic phases were measured. (C) 1999 American Institute of Physics. [S1063-7834(99)02907-X].