High-field magnetization ofS=1antiferromagnetic bond-alternating chain compounds

Abstract

High-field magnetization and susceptibility measurements have been performed on Sϭ1 antiferromagnetic bond-alternating chain compounds: ͓Ni 2 (dpt) 2 (-ox)(-N 3 )͔(PF 6 ) ͓dptϭbis͑3-aminopropyl͒amine, oxϭ C 2 O 4 ] ͑abbreviated as NDOAP͒ and ͓Ni͑333-tet͒(-NO 2 )]ClO 4 ͓333-tetϭN,NЈ-bis͑3-aminopropyl͒-1,3-propanediamine͔ ͑abbreviated as NTENP͒. The magnetization of NDOAP shows two steep increases at about 200 and 500 kOe. A magnetization plateau is observed between about 300 and 500 kOe, corresponding to half the value of the saturation moment. Comparison between numerical calculations and the experimental results, including the magnetic susceptibility, shows that NDOAP has a singlet ground state due to dimerization with a bond-alternating ratio ␣ϭ0.1. The half-saturation plateau is also observed around 700 kOe in the magnetization of NTENP. The magnetization process of NTENP is well reproduced by the numerical result calculated for the parameter of ␣ϭ0.45 in the singlet-dimer phase. The ␣ dependence of the magnetization processes is discussed.

Dynamical properties ofS=1bond-alternating Heisenberg chains in transverse magnetic fields

“…The system shows a quantum phase transition between the Haldane-gap phase and the dimer phase depending on the bond-alternating ratio [1]. Thermodynamic properties at the gapless point [2,3] and in the dimer phase [4,5,6,7] were studied experimentally. The results were compared with theoretical results and good agreement was obtained [2,3,4,5,7].…”

“…Thermodynamic properties at the gapless point [2,3] and in the dimer phase [4,5,6,7] were studied experimentally. The results were compared with theoretical results and good agreement was obtained [2,3,4,5,7]. The elementary excitation was investigated by quantum Monte Carlo [8] and exact diagonalization [9] methods.…”

Spin dynamics of the half-magnetization plateau in S = 1 bond-alternating spin chains

“…For some S=1 bond-alternating spin-chain compounds in the dimer phase, [Ni 2 (dpt) 2 (μ-ox)(μ-N 3 )]PF 6 (abbreviated to NDOAP), [Ni(Medpt) 2 (μ-ox)(μ-N 3 )]ClO 4 · 0.5H 2 O (NMOAP), and [Ni(C 9 H 24 N 4 )(NO 2 )]ClO 4 (NTENP), where dpt = bis(3-aminopropyl)amine, ox = C 2 O 4 and Medpt=methyl-bis(3-aminopropyl)amine, the half-magnetization plateaus were observed at 30T-40T, 40T-55T and ∼70T, respectively [5,6]. Quite recently, inelastic neutron-scattering measurements for NTENP were performed in magnetic fields up to 14.5T.…”

Fractional magnetization plateaus of the spin-12Heisenberg orthogonal-dimer chain: Strong-coupling approach developed from the exactly solved Ising-Heisenberg model

“…From the experimental point of view, the fractional plateaux have been detected in magnetization curves of a variety of insulating magnetic materials, which mostly provide real-world representatives of zero-dimensional Heisenberg spin clusters 4-10 , one-dimensional Heisenberg spin chains [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] or twodimensional Heisenberg spin lattices [28][29][30][31][32][33][34][35][36] . The fractional magnetization plateaux of onedimensional quantum Heisenberg chains should satisfy the quantization condition p(S u − m u ) ∈ Z (p is a period of the ground state, S u and m u are the total spin and total magnetization per elementary unit, Z is a set of the integer numbers), which has been derived by Oshikawa, Yamanaka, Affleck (OYA) by extending the Lieb-SchultzMattis theorem [37][38][39] .…”

“…To the best of our knowledge, all intermediate plateaux of the quantum Heisenberg chains observed to date experimentally are in agreement with the OYA rule when assuming either simple period p = 1 or just the period doubling p = 2. For instance, the experimental representatives of the spin-1/2 Heisenberg diamond chain [11][12][13] , the trimerized spin-1/2 Heisenberg chain [14][15][16] and the mixed spin-(1/2,1) Heisenberg chain 17 display one-third plateau, the experimental realizations of the tetramerized spin-1/2 Heisenberg chain [18][19][20] , the spin-1/2 Heisenberg bond alternating chain 21 as well as the spin-1 Heisenberg bond alternating chain 22 exhibit one-half plateau, the experimental realization of the spin-1 Heisenberg ladder 23,24 shows one-quarter plateau, etc.…”