Ferrimagnetic states in S = 1/2 frustrated Heisenberg chains with period 3 exchange modulation

Abstract

The ground state properties of theS = 1/2 frustrated Heisenberg chain with period 3 exchange modulation are investigated using thenumerical diagonalization and density matrix renormalization group (DMRG) method. It isknown that this model has a magnetization plateau at one third of the saturation magnetizationMs. On the other hand, the ground state is ferrimagnetic even in the absence offrustration if one of the nearest neighbour bond is ferromagnetic and the othersare antiferromagnetic. In the present work, we show that this ferrimagneticstate continues to the region in which all bonds are antiferromagnetic if thefrustration is strong. This state further continues to the above-mentioned1/3 plateau state. In between, we also find the noncollinear ferrimagneticphase in which the spontaneous magnetization is finite but less thanMs/3. The intuitive interpretation for the phase diagram is given and the physical properties ofthese phases are discussed.