Weak ferromagnetism in CuB2O4 copper metaborate

The results of the magnetic susceptibility, magnetization, specific heat an d mu SR measurements of the tetragonal CuB2O4 single crystals are presented . CuB2O4 is a paramagnet at temperatures above 21 K. The paramagnetic Neel temperature and effective magnetic moment determined from high-temperature magnetic susceptibility measurements are equal to theta = -9.5 K, mu(eff) = 1.77 mu(B), respectively. The easy plane magnetic structure with a weak sp ontaneous magnetic moment was determined in the temperature range 21-10 K. The value of the weak spontaneous magnetic moment is m(0) = 0.56 emu/g at T = 10 K. Morin magnetic phase transition was observed at the temperature T- M = 10 K. The mu SR measurements confirm the existence of two magnetic phas e transition at T = 21 and 10 K. (C) 1999 Elsevier Science B.V. All rights reserved.