Magnetic critical behavior in the[Cu(1−hydroxybenzotriazolate)2(MeOH)

Abstract

H nuclear-magnetic-resonance and magnetization measurements have been performed in the moleculebased solid ͓Cu(btaO) 2 (MeOH)͔ n ͑btaOH stands for 1-hydroxybenzotriazolate͒ as a function of temperature. The compound exhibits a critical transition at T c ϭ5.7 K from a high-temperature paramagnetic phase to a low-temperature magnetic phase characterized by relatively strong ferromagnetic interactions. The experimental results are best analyzed considering that the ground state of the system is a random-field ferromagnetic state in the absence of an external magnetic field. The dynamics of the electronic-spin fluctuations in the low-temperature magnetic phase are estimated using a two-level system model.