Observation of the Neel state in doped CuGeO<sub>3</sub>

Lussier, J. G.; Coad, S.; McMorrow, D. F.; Paul, Daniel

doi:10.1088/0953-8984/7/25/003

Cited by 76 publications

(83 citation statements)

References 13 publications

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“…Investigations have concentrated on systems where Cu atoms were replaced with Zn [14][15][16][17][18][19] or Ge was replaced with Si. [20][21][22] It is now well established that a new antiferromagnetic (AF) ordered phase appears at low temperatures in both Zn-doped 14,19 and Si-doped 22 samples.…”

Section: Introductionmentioning

confidence: 99%

Spin-Peierls and antiferromagnetic phases in Cu1−xZnxGeO
Martin
¹
,
Hase
²
,
Hirota
³

et al. 1997
Phys. Rev. B

116

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Comprehensive neutron scattering studies were carried out on a series of high-quality single crystals of Cu 1−x Zn x GeO 3 . The Zn concentration, x, was determined for each sample using Electron Probe Micro-Analysis. The measured Zn concentrations were found to be 40-80% lower than the nominal values. Nevertheless the measured concentrations cover a wide range which enables a systematic study of the effects due to Zn-doping. We have confirmed the coexistence of spin-Peierls (SP) and antiferromagnetic (AF) orderings at low temperatures and the measured phase diagram is presented. Most surprisingly, long-range AF ordering occurs even in the lowest available Zn concentration, x=0.42%, which places important constraints on theoretical models of the AF-SP coexistence. Magnetic excitations are also examined in

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Section: Introductionmentioning

confidence: 99%

Spin-Peierls and antiferromagnetic phases in Cu1−xZnxGeO
Martin
¹
,
Hase
²
,
Hirota
³

et al. 1997
Phys. Rev. B

116

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“…The effect of impurities on CuGeO 3 has been investigated using neutron scattering [14,15], magnetic susceptibility measurements [14,16], specific heat measurements [17], and spin electron resonance [18]. The main results of these studies are the collapse of the spin gap [14,16], and the competition between the SP and the Néel states [14,17], when a small amount of impurities is introduced. From the theoretical point of view, the introduction of non-magnetic impurities, which for the nearest-neighbors Heisenberg model leads to the appearance of chains with open boundary conditions (OBC), has been analyzed using conformal field theory and Monte Carlo simulations [19,20].…”

Section: Introductionmentioning

confidence: 99%

Effect of spin-1 impurities in dimerized Heisenberg chains

et al. 1998

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The effects of spin-1 impurities introduced in dimerized antiferromagnetic spin chains are studied using Lanczos diagonalization and quantum Monte Carlo simulations. Firstly, the magnitude of the interaction between a Ni-ion replacing a Cu-ion is derived for the case study system Cu-O-Cu. Then, it is shown that the introduction of S = 1 impurities leads to the suppression of the original spin gap of the dimerized system and to the enhancement of the antiferromagnetic correlations close to the impurity. These features are interpreted in terms of a valence bond picture of the ground state of both the pure and the doped system. The similitudes and differences between the underlying mechanisms that produce these effects in the cases of nonmagnetic and S = 1 impurities are analyzed. It is stressed that a singlet formed between the spin-1 impurity site and the two spin-1/2 neighbors spins behaves as an effective nonmagnetic vacancy which may be partially responsible for the enhancement of the antiferromagnetic correlations on the whole system. Implications of these results for experiment are also discussed.

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“…4 -10͒ or Zn, Ni, or Mg for Cu, 4,5,8,11 leads to the appearance of AF long range order ͑LRO͒ that may coexist with spinPeierls order ͑or dimerization͒ below a Néel ordering temperature T N . Increasing the doping level can drive the spinPeierls transition temperature T sP to zero, while T N remains finite; eventually strong enough doping suppresses both spinPeierls and Néel ordering in the system.…”

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confidence: 99%

Bond-randomness-induced Néel order in weakly coupled antiferromagnetic spin chains

Joshi

Yang

2003

Phys. Rev. B

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Quasi-one-dimensional antiferromagnetic ͑AF͒ quantum spin systems show a wide range of interesting phenomena such as the spin-Peierls transition and disorder driven long-range ordering. While there is no magnetic long-range order in strictly one-dimensional systems, in real systems some amount of interchain coupling is always present and AF long-range order may appear below a Néel ordering temperature T N . We study the effect of bond randomness on Néel ordering in weakly coupled random AF Sϭ1/2 chains, both with and without dimerization ͑or spin-Peierls order͒. We use the real space renormalization group method to tackle the intrachain couplings, and a mean-field approximation to treat the interchain coupling. We show that in the nondimerized chain, disorder ͑represented by bond randomness͒ enhances the Néel order parameter; in the dimerized chain which shows no magnetic ordering in the weak interchain coupling limit without randomness, disorder can actually lead to long range order. Thus disorder is shown to lead to, or enhance the tendency toward long range order, providing another example of the order-by-disorder phenomenon. We make a qualitative comparison of our results with the observed phenomenon of doping induced long-range ordering in quasi-one-dimensional spin systems such as CuGeO 3 . Quasi-one-dimensional quantum spin systems have been under intense theoretical and experimental investigation over the past few decades.1 These systems show a wide range of interesting and unexpected phenomenon such as the spinPeierls transition and disorder driven long-range ordering.2-11 In strictly one-dimensional systems, there is no long-range magnetic order due to strong quantum and thermal fluctuations. However in real systems, such as CuGeO 3 , KCuF 3 , or Sr 2 CuO 3 some amount of interchain coupling is always present. 3,12,13 In these cases magnetic long range order may appear below a Néel ordering temperature T N . In this work we study the effect of disorder on long range ordering in weakly coupled spin chains. We show that disorder leads to, or enhances the tendency toward long-range order, providing another example of the order-by-disorder phenomenon that has received considerable attention in recent years.14 The disorder driven long-range ordering seen here is purely quantum mechanical in origin, as opposed to being thermally driven.14 The specific example that we bear in mind in our study is the interesting phenomenon of doping driven long range ordering observed in the spin-Peierls material CuGeO 3 . In this system the Cu ions form an effective one-dimensional ͑1D͒ antiferromagnetic ͑AF͒ spin-1/2 chain with weak interchain coupling. This is the first inorganic system to show the spinPeierls transition.3 Surprisingly, while the pure system has no magnetic order in the ground state, doping the system with a very small amount of impurities, such as Si for Ge ͑Refs. 4 -10͒ or Zn, Ni, or Mg for Cu, 4,5,8,11 leads to the appearance of AF long range order ͑LRO͒ that may coexist with spinPeierls order ͑or dimer...

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Observation of the Neel state in doped CuGeO₃

Cited by 76 publications

References 13 publications

Spin-Peierls and antiferromagnetic phases in Cu1−xZnxGeO
Martin
¹
,
Hase
²
,
Hirota
³

et al. 1997
Phys. Rev. B

Spin-Peierls and antiferromagnetic phases in Cu1−xZnxGeO
Martin
¹
,
Hase
²
,
Hirota
³

et al. 1997
Phys. Rev. B

Effect of spin-1 impurities in dimerized Heisenberg chains

Bond-randomness-induced Néel order in weakly coupled antiferromagnetic spin chains

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Observation of the Neel state in doped CuGeO3

Cited by 76 publications

References 13 publications

Spin-Peierls and antiferromagnetic phases in Cu1−xZnxGeOMartin1, Hase2, Hirota3 et al. 1997Phys. Rev. B

Spin-Peierls and antiferromagnetic phases in Cu1−xZnxGeOMartin1, Hase2, Hirota3 et al. 1997Phys. Rev. B

Effect of spin-1 impurities in dimerized Heisenberg chains

Bond-randomness-induced Néel order in weakly coupled antiferromagnetic spin chains

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Observation of the Neel state in doped CuGeO₃

Spin-Peierls and antiferromagnetic phases in Cu1−xZnxGeO
Martin
¹
,
Hase
²
,
Hirota
³

et al. 1997
Phys. Rev. B

Spin-Peierls and antiferromagnetic phases in Cu1−xZnxGeO
Martin
¹
,
Hase
²
,
Hirota
³

et al. 1997
Phys. Rev. B