Magnetic Field dependence of specific heat in Clinoatacamite Cu2Cl(OH)3

Abstract

We have measured the magnetic field dependence of the specific heat up to H=6 T in a geometrically frustrated magnet, clinoatacamite Cu2Cl(OH)3, with the corner-sharing tetrahedron structure of the Cu2+ ions. At H=0 T, the specific heat exhibits two anomalies at T1=6.2 K and at T2=18.1 K T1 shows a reentrant behavior in the T - H phase diagram, while T2 shows a gradual decrease with increasing magnetic fields. The field dependence of T1 and T2 may reflect different aspects of two transitions. The transition at T1 is related with the two dimensional nature of the kagome antiferromagnets which are weakly coupled via Cu2+ ions at the triangular sites located in between the kagome layers, while that at T2 represents the feature in a conventional long-range ordering.