Decomposition of the spin-1/2 Heisenberg chain compound Sr2CuO3 in air and water:: An EPR and magnetic susceptibility study of Sr2Cu(OH)6 -: art. no. 134428

The reaction of Sr2CuO3 with air and water was studied to address the origin of the reported variable Curie-Weiss impurity contribution to the magnetic susceptibility chi of this compound at low temperatures. Sr2CuO3 was found to decompose upon exposure to either of these environments. The compound Sr2Cu(OH)(6) was identified as the primary reaction product. A pure sample of Sr2Cu(OH)(6) was then prepared separately. Electron paramagnetic resonance, isothermal magnetization versus magnetic field [M(H)], and chi versus temperature T measurements demonstrate that Sr2Cu(OH)(6) contains weakly interacting Cu2+ magnetic moments with spin S=1/2 and average g factor equal to 2.133. From a fit of chi(T) by the Curie-Weiss law and of the M(H) isotherms by modified Brillouin functions, the exchange interaction between adjacent Cu2+ spins was found to be J/k(B)=1.06(4) K, a weakly antiferromagnetic interaction. Our results indicate that the previously reported, strongly sample-dependent, Curie-Weiss contribution to chi(T) of a polycrystalline Sr2CuO3 sample most likely arises from exposing the sample to air, resulting in a variable amount of paramagnetic Sr2Cu(OH)(6) on the surface of the sample.