ESR of “the Magnetic Dangling Bond” in the Haldane State

Effect of vacancy doping on the Haldane spin-liquid state inPbNi2−xMgxZorko1, Arčon2, Lappas3 et al. 2002Phys. Rev. B

“…We note that in the high-temperature region ͑i.e., TϾ⌬͒ a very similar ESR signal was also observed in other Haldane systems like ͓Ni͑C 2 H 8 N 2 ) 2 (NO 2 )]ClO 4 ͑NENP͒ for example. 11,12 The signal was attributed to the exchangeamalgamated paramagnetic resonance, whose fine structure from the single-ion anisotropy D is averaged by the strong intrachain exchange interaction. Due to the many similarities of the high-temperature ESR line in NENP and PbNi 2Ϫx Mg x V 2 O 8 samples, we believe that its origin is the same in the two systems.…”

“…Such a behavior was indeed observed in nonmagnetically doped Haldane systems. 14,18 On the other hand, if the broadening was due to the interaction between the Sϭ 1 2 spins either adjacent to the Mg 2ϩ impurity or to a spin Sу1, terms of the type DS Z 2 would be added to spin Hamiltonian and to a first order the ESR broadening would be independent of microwave frequency. The conclusion at this point is thus that our ESR signal cannot be attributed to isolated Sϭ 1 2 spins around Mg 2ϩ impurities.…”

Magnetic interaction between impurity and impurity-liberated spins in the doped Haldane chain compoundsPbNi2−xAxV2Zorko1, Arčon2, Lappas3 et al. 2006Phys. Rev. B4050View full textAdd to dashboardCite

“…In fact, also in NENP it has been reported that nonmagnetic impurities do not induce substantial broadening of the X-band ESR spectra at high temperatures. 32 One should note that the interchain coupling in NENP is significantly smaller than in PbNi 2 V 2 O 8 .…”

Magnetic studies of end-chain spin effects in the Haldane-gap materialNi(C3H10Granroth1, Maegawa2, Meisel3 et al. 1998Phys. Rev. B170140View full textAdd to dashboardCite

“…An even/odd chain length effect is not expected for chains longer than ϳ50 spins, 15,16 and the data of Ramirez, Cheong, and Kaplan 14 have been described by Sϭ 1 2 end-chains experiencing a strong anisotropy. 17,18 Although subsequent experiments [19][20][21] have been interpreted in terms of Sϭ 1 2 end-chains, these studies have not conclusively eliminated the Sϭ1 possibility. The Haldane-gap material Ni(C 3 H 10 N 2 ) 2 N 3 (ClO 4 ) ͑NINAZ͒ ͑Ref.…”

“…Once again, due to its properties, undoped NINAZ is ideally suited to observe this phenomenon, and this paper provides experimental evidence of these fundamental interactions. In many instances, nonmagnetic dopants are used to increase the end-chain spin concentration, 13,14,17,[19][20][21]23,24 but unfortunately, doped samples have their limitations. For example in NENP doped beyond ϳ0.5%, the dopant no longer breaks chains by direct substitution.…”