S=1/2 Heisenberg J1-J2 chain antiferromagnets have been investigated extensively due to their exotic magnetic states. Here, we report the magnetic behavior of birchite Cd2Cu2(PO4)2SO4·5H2O and its effective spin model. Experimental studies by magnetic susceptibility, magnetization, heat capacity, and μSR measurements indicate the absence of long-range order down to 0.4 K. Theoretical studies reveal that birchite is a model compound for the J1-J2 antiferromagnetic chain: the intrachain interactions J1 and J2 are antiferromagnetic and their magnitude is about 100 times larger than the interchain interactions. The magnitude of J2 is two to three times larger than that of J1, thus the spin gap is expected to be only a few percent of that of J1. The temperature dependence of the specific heat shows a broad peak at about 1 K (≃0.036J1), which suggests the presence of a spin gap.
ASJC Scopus subject areas
- Materials Science(all)
- Physics and Astronomy (miscellaneous)