Synthesis and magnetic properties of Cu3B2O6 single crystals

The temperature dependence of the magnetic susceptibility of Cu3B2O6 single crystals grown by spontaneous crystallization from a melt consisting of a mixture of CuO and B2O3 and the behavior of their magnetization are investi gated in magnetic fields up to 55 kOe. A broad susceptibility maximum is ob served near 39 K, and a sharp drop in susceptibility is observed at T<10 K. The paramagnetic Neel temperatures for all orientations of the magnetic fi eld in the crystal investigated are negative, attesting to the predominantl y antiferromagnetic character of the exchange interactions. The effective m agnetic moment of the Cu2+ ion is anisotropic and lies in the range from 1. 054 mu(B) to 1.545 mu(B). The magnetization depends linearly on magnetic fi eld at T>10 K, whereas at temperatures below 10 K a discontinuity is observ ed at fields of the order of 40 kOe. At room temperature, electron magnetic resonance characterized by an almost isotropic g factor (g=2.165) is detec ted at 36.22 GHz. The exchange interactions in Cu3B2O6 are analyzed on the basis of the Goodenough-Kanamori rules. The possibility of the establishmen t of a singlet magnetic state in the crystal is analyzed. (C) 1999 American Institute of Physics. [S1063-7834(99)02404-1].