Quasi-one-dimensional Heisenberg antiferromagnetic model for an organic polymeric chain

Abstract

Using the exact diagonalization technique, we study the properties of the ground state of a spin- antiferromagnetic Heisenberg model for a zigzag polymer chain with side radicals connected to the even sites. We consider the nearest-neighbour exchange J and the next-nearest-neighbour exchange αJ along the main chain, and J1 between the even site on the main chain and the radical site. For small α the ground state is ferrimagnetic. For α>αc 1, the ground state is a spiral phase, which is characterized by a peak of the static structure factor S(q) locating at an incommensurate value qmax. For α>αc 2, the ground state is antiferromagnetic. With increasing J1, αc 1 decreases while αc 2 has a maximum at about J1 = 0.5. For very small J1 and α = 0.5, the spin configuration on the main chain is a product of nearest-neighbour singlets. In the antiferromagnetic phase, if J1 is large enough the even site and the radical site form a singlet with exchange-decoupling from the odd site while the odd sites approximately form an antiferromagnetic chain.

Field-controlled magnetic order with insulator–metal transitions in a periodic Anderson-like organic polymer

“…Due to quantum effect and ferromagnetic properties, the lowdimensional organic magnets have attracted considerable attention both by chemists and physicists in recent years. [1][2][3][4][5][6][7][8][9][10][11][12][13] Besides, the nonlinear optical coefficients and transport properties significant for molecular electronics of low-dimensional quantum systems were also investigated by Pati et al [14][15][16][17][18][19][20][21] As far as we know, several quasi-one-dimensional organic ferromagnets have been synthesized experimentally such as poly-BIPO, 1 p-NPNN 2 and poly(9,10-anthryleneethynylene) 6 with pendant radicals. Subsequently, some theoretical models 4,5,22 were proposed to describe the quasi-one-dimensional conjugated organic polymer, which was considered as a delocalized p-electron system, where the orbitals of successive carbon atoms overlap, giving rise to charge mobility along the backbone of the polymer chain.…”

Asymmetrical Elementary Excitations Responsible for the Ferrimagnetism in an Antiferromagnetic Spin-1/2 Zigzag Ladder

“…Even though many spin-chain models have been extensively studied from experimental and theoretical points of view, one-dimensional (1D) quantum spin systems are still an attractive field in low-dimensional quantum magnetism because of their distinctive physical properties. The S=1/2 zigzag spin chain with the nearest-neighbor (NN) and next-nearest-neighbor (NNN) exchange interactions has long attracted considerable attention [1][2][3][4][5][6][7]. One important reason is that the competition between the NN and NNN exchange interactions gives rise to various intriguing phenomena and potentially rich properties in these spin systems, such as a Haldane state in a spin-1 chain [8], a dimer state in a spin-1/2 chain with bond alternation [9][10][11] and a strong frustrated spin chain [1,2].…”