  Specific heat and magnetization measurements of the compound
[Cu2(apyhist)2Cl2](ClO4)2, where apyhist =
(4-imidazolyl)ethylene-2-amino-1-ethylpyridine), were used to identify a
magnetic-field-induced long-range antiferromagnetic ordered phase at low
temperatures (T < 0.36 K) and magnetic fields (1.6 T < H < 5.3 T). This system
consists of a Schiff base copper(II) complex, containing chloro-bridges between
adjacent copper ions in a dinuclear arrangement, with an antiferromagnetic
intradimer interaction |Jintra|/kB = 3.65 K linked by an antiferromagnetic
coupling |Jinter|z/kB = 2.7 K. The magnetic-field-induced ordering behavior was
analyzed using the mean field approximation and Monte Carlo simulation results.
The obtained physical properties of the system are consistent with the
description of the ordered phase as a Bose-Einstein Condensation (BEC) of
magnetic excitations. We present the phase diagram of this compound, which
shows one of the lowest critical magnetic field among all known members of the
family of BEC quantum magnets.
