First Study of Nuclear Antiferromagnetism by Neutron Diffraction

Roinel, Y.; Bouffard, V.; Bacchella, G.L.; Pinot, M.; Meriel, P.; Roubeau, P.; Avenel, O.; Goldman, M.; Abragam, A.

doi:10.1103/physrevlett.41.1572

Cited by 41 publications

(22 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Of course, conclusive evidence of an antiferromagnetic transition can only be obtained from neutron diffraction studies, as in the case of LiH. 3 In search of a transition we have made NMR measurements with both transverse and longitudinal geometries (cf. Section 3).…”

Section: Search For a Transitionmentioning

confidence: 99%

“…Both ferromagnetic and antiferromagnetic structures have been found, and the ordering has been verified by observing the NMR frequency shift of dilute probe nuclei in the ferromagnetic case 2 and by neutron diffraction studies in the antiferromagnetic case. 3 We have extended these studies to the nuclear spin system in a metal by performing measurements on copper; so far, apart from more recent studies of PrCu6, which is a van Vleck paramagnet, ~ this is the only metal investigated. In our case the experimental technique of the Saclay group is no longer applicable, because eddy currents in the metallic sample would shield the nuclei against both the polarizing and demagnetizing ac fields.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

NMR studies on nuclear ordering in metallic copper below 1 ?K

et al. 1980

View full text Add to dashboard Cite

The nuclear spin system of metallic copper in a polycrystalline sample consisting of thin wires has been studied using a cryostat in which a dilution refrigerator and two copper nuclear stages operate in series. The spin system was cooled to 50 nK, which is an all-time low-temperature record. The NMR absorption curves were measured in external fields from zero to B~x, = I5 mT and at entropies corresponding to polarizations up to 0.9. The line shapes reveal the effect of indirect exchange interaction corresponding to an antiferromagnetic value of ~j Jii/'y~12~op = -0.42 + 0.05. This result was obtained both from the interference of the isotopic absorption lines at 15 m T and from the shift of the second harmonic in fieMs below 2 mT. Thus, an antiferromagnetic transition in zero field at about200 nK is expected. The Curie-Weiss 8 points to a transition temperature of 150nK; the int, erse static susceptibility vs temperature curve clearly predicts antiferromagnetism. However, no evidence of such a transition was found in NMR spectra measured with the excitation transverse to the copper wires, although the entropy was reduced to about 0.45R In 4, with the corresponding temperatures well below I00 nK. On the other hand, in measurements during which the excitation was parallel to the wires, a clear saturation of susceptibility to a constant value could be seen as a sudden change in the apparent relaxation rate at the lowest entropies.

show abstract

Section: Search For a Transitionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

NMR studies on nuclear ordering in metallic copper below 1 ?K

et al. 1980

View full text Add to dashboard Cite

show abstract

“…For nuclear magnets it is the spin-dependent part of the nuclear cross section which makes possible the determination of ordered spin arrangements. 5 The previous neutron-scattering studies of nuclear ordering comprise the work on LiH by Roinel et al 6 and on 3 He by Benoit et al 1 In these two systems the experimental conditions and the physics of ordering are very different from those in copper. After demagnetization in the rotating frame LiH orders in a strong magnetic field, and in 3 He the ordering is due to particle exchange, which is a strong quantum effect.…”

mentioning

confidence: 98%

Observation of Nuclear Antiferromagnetic Order in Copper by Neutron Diffraction at Nanokelvin Temperatures

Ta¹,

Mt²,

Ov³

et al. 1988

Phys. Rev. Lett.

View full text Add to dashboard Cite

Long-range nuclear antiferromagnetic order in the nuclear-spin system of a 65 Cu single crystal has been observed by neutron diffraction. By use of a linear position-sensitive detector, the time evolution of the antiferromagnetic (100) Bragg peak was followed during the warmup of the nuclear-spin system. The peak intensity was found to depend strongly on the external magnetic field between 5=0 and the critical field B c =0.25 mT.PACS numbers: 72.25. +Z, 61.12.Gz, 75.30.Kz, 75.50.Ee In this Letter we report the first observation of spontaneous nuclear order in an elemental metal by neutron diffraction. Our study was made on a 65 Cu single crystal. Since the ordering takes place at about 60 nK, a new temperature regime has been opened for neutron diffraction experiments.Elemental copper represents one of the simplest systems for the study of nuclear magnetism. It is a well understood metal, and the nuclear spins interact via the known dipolar and indirect conduction-electron-mediated Ruderman-Kittel interactions. In general, nuclear magnetism differs from its electronic counterpart in several important ways: The nuclear magnetic moments are highly localized and thus represent point probes for the interactions, the energy scale of importance is extremely small, and, hence, the critical temperature of the spontaneous nuclear ordering is lowered by several orders of magnitude. Finally, at low temperatures the nuclear-spin system in copper is only weakly coupled to the lattice; thus the nuclear spins can be cooled to the ordered state by adiabatic demagnetization while the lattice and the conduction electrons are kept at a relatively high temperature.Experimental evidence for spontaneous antiferromagnetic ordering in copper was found in studies of the lowfrequency ac susceptibility on a polycrystalline sample at temperatures below TN ~ 60 nK. x In later experiments on a single crystal, all three Cartesian components were studied, and an entropy-field phase diagram was deduced. 2 It showed three distinct regions and an upper critical field of 0.25 mT. The theoretical aspect of these results has been dealt with in a series of papers, 3 but none of them has provided a full understanding of the phase diagram. An interesting aspect is connected with the fee structure, which may lead to frustrated spin configurations. 4 For a full understanding of any magnetic system it is fundamental to establish the magnetic ground state. For this purpose neutron diffraction is unique. For nuclear magnets it is the spin-dependent part of the nuclear cross section which makes possible the determination of ordered spin arrangements. 5 The previous neutron-scattering studies of nuclear ordering comprise the work on LiH by Roinel et al. 6 and on 3 He by Benoit et al 1 In these two systems the experimental conditions and the physics of ordering are very different from those in copper. After demagnetization in the rotating frame LiH orders in a strong magnetic field, and in 3 He the ordering is due to particle exchange, which is a strong quan...

show abstract

“…He thus treated cross-relaxation induced by cross-correlation [4], relaxation in the presence of off-resonance rf irradiation [5,6], chemical exchange [7] or the derivation of the general theory of relaxation valid at any temperature [8]. His broad interest has led him also to relaxation [9] and NMR lineshape in solids [10], to magic angle spinning NMR experiments in solids [11,12], to polarized neutrons [13], to the effect of dipolar fields in liquids [14], to the study of polymers [15], or to the effect of mechanical rotations on the measured NMR frequency [16][17][18]. More recently, as an scientific adviser to Amersham Health, he is exploiting his knowledge on the foundations of NMR for applications in MRI.…”

mentioning

confidence: 99%

“…[5,6], de l'échange chimique [7] ou encore de la théorie de la relaxation valable pour toute température [8]. Son vaste intérêt pour les méthodes de résonance en général l'a également conduit à travailler sur la relaxation [9] et la forme de raie [10] en RMN du solide, la RMN des échantillons solides tournant à l'angle magique [11,12], les neutrons polarisés [13], l'effet du champ dipolaire dans les liquides [14], les polymères [15] ou encore les changements de fréquences induits par la rotation de l'échantillon [16][17][18]. Depuis peu, il est conseiller scientifique chez Amersham Health où il utilise sa connaissance des fondements de la RMN à des fins d'applications en IRM.…”

unclassified

Foreword

Desvaux

2004

Comptes Rendus. Physique

View full text Add to dashboard Cite

ForewordNuclear magnetic resonance (NMR) has been discovered more than fifty five years ago. Since then, its field of application has grown continuously, reaching domains as different as food science, petroleum exploration, medicine or quantum computing. Indeed, NMR can provide valuable information in many domains, since almost all atoms have at least one isotope with a nuclear magnetic moment (non-vanishing nuclear spin), since little energy is involved and since, finally, the coupling between the nuclear spins and the surroundings is sufficiently small to be treated as a perturbation. This explains the capability of NMR to explore the core of matter through local probes at an atomic resolution. Even if magnetic resonance is sensitive to the local environment, NMR spectra still reveal the long range symmetry of the sample, allowing its use for characterizing ordered, disordered or partially ordered systems. It is certainly as an analytical method that NMR has experienced the largest extension (R.R. Ernst, Nobel Prize for Chemistry 1991), illustrated nowadays by the presence of spectrometers in almost all chemistry laboratories. Other applications of NMR were recently recognized through Nobel prizes. Firstly, NMR has now been proved to be a real alternative to X-ray crystallography for determining the solution structure of biomolecules such as proteins or DNA fragments, with the key advantage of allowing the exploration of their internal dynamics (K. Wűthrich, Nobel Prize for Chemistry 2002). Secondly, NMR has reached hospital world through its non-invasive imaging feature, becoming a very important diagnosis tool in medicine (P.C. Lauterbur and P. Mansfield, Nobel Prize for Medecine 2003).Even if NMR is now used in many fields, the concepts of NMR originate from the physics of condensed matter. The present special issue of the Comptes Rendus Physique mainly focuses on two connected axes of active research in physics: highly polarized nuclear spin systems and dipolar interactions. This issue follows a symposium held 10 March 2003 at CEA/Saclay in the honor of the 70th birthday of Maurice Goldman. This symposium comprised different conferences on fields connected to NMR such as polymers, magnetic resonance imaging or quantum computers.Maurice Goldman has worked for more than forty years in the field of NMR in condensed matter physics and made many important contributions to the two domains presented in this special issue. He was introduced to NMR by Anatole Abragam and became rapidly a specialist in relaxation theory and nuclear magnetism. He was one of the predominant contributors to the creation of spin thermodynamics applied to nuclear magnetic resonance in solids through the spin temperature concept [1]. Then Maurice Goldman played a key-role in the description and observation of the phase transition experienced by highly polarized nuclear spins to ferro-, heli-or antiferromagnetic states, the bilinear interactions between the spins being the dipolar interactions [2]. His achievement in the field of nuclear ma...

show abstract

First Study of Nuclear Antiferromagnetism by Neutron Diffraction

Cited by 41 publications

References 2 publications

NMR studies on nuclear ordering in metallic copper below 1 ?K

NMR studies on nuclear ordering in metallic copper below 1 ?K

Observation of Nuclear Antiferromagnetic Order in Copper by Neutron Diffraction at Nanokelvin Temperatures

Foreword

Contact Info

Product

Resources

About