Effects of high pressure on A2Cu2Mo3O12(A=Rb,Cs): A one-dimensional system with competing ferromagnetic and antiferromagnetic interactions

We report magnetic susceptibility χ(T) and magnetization M(H) in A2Cu2Mo3O12 (A=Rb, Cs) under hydrostatic pressures. χ(T) shows a broad peak at low temperatures. When the pressure is applied to the Rb compound, the peak in χ(T) grows and shifts to a lower temperature, the M(H) curve becomes steeper, and the saturation field decreases. Comparing with the calculation of χ(T) by DMRG method, accompanied with a correction term (∝1/T), these are qualitatively explained by a decrease of |α|, where α is the ratio between the nearest-neighbor and the next-nearest-neighbor interactions. |α| is reduced approximately by 0.01 per 1GPa. The Cs compound has a different pressure dependence from the Rb compound