Nuclear spin-lattice relaxation of the Zeeman and the spin-spin systems in copper between 1 and 17 mK

Aalto, M.I.; Berglund, P.; Collan, H.; Ehnholm, Gösta; Gylling, R.G.; Lounasmaa, O. V.

doi:10.1016/0031-8914(72)90077-8

Cited by 4 publications

(4 citation statements)

References 6 publications

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“…The early version of the second nuclear stage, i.e., the sample, was made of 2000 copper wires, 0.04 mm in diameter and insulated by oxidation; the measured residual resistivity ratio RRR=200. 3 This wire was chosen because its spin-lattice relaxation time had previously been measured (Aalto et al, 1972). The weight of the sample was 2 g. At their upper ends, the thin copper wires were welded together and connected to the first nuclear stage by means of copper foils, without any heat switch.…”

Section: B Helsinki Cryostatmentioning

confidence: 99%

Nuclear magnetic ordering in simple metals at positive and negative nanokelvin temperatures

1997

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This paper is a comprehensive review of almost twenty years of research on nuclear magnetic ordering, first in copper and later in silver and rhodium metals. The basic principles of nuclear magnetism and the measurement of positive and negative spin temperatures are discussed first. Cascade nuclear refrigeration techniques, susceptibility and nuclear-magnetic-resonance (NMR) measurements, and arrangements for neutron-diffraction experiments at nanokelvin and picokelvin temperatures are described next. Comprehensive magnetic-susceptibility and neutron-diffraction measurements on copper, which led to the discovery of at least three antiferromagnetic phases, one displaying the novel (0 2 3 2 3 ) spin structure and the other two showing the type-I order of the fcc system, are then described in detail. NMR data on silver, at TϾ0 and TϽ0, are presented next leading to the observation that silver orders antiferromagnetically at positive spin temperatures and ferromagnetically at negative spin temperatures. The authors discuss recent neutron-diffraction measurements that show that the antiferromagnetic structure at TϾ0 is in a single-k type-I state. NMR data on rhodium at TϾ0 and TϽ0 are also described. Results obtained on Tl, Sc, AuIn 2 , and metallic Pr compounds and on insulators like CaF 2 are then discussed briefly. The paper is concluded by an extensive theoretical section. Calculations of conduction-electron mediated exchange interactions are described, and the mean-field theory of nuclear magnetic ordering is presented. The role of thermal and quantum fluctuations is then discussed, particularly in the selection of the antiferromagnetic ground state. Finally, theoretically calculated magnetic phase diagrams and ordered spin structures of copper and silver are presented in detail and compared with experimental results. The overall agreement is good, affirming the value of nuclear magnets in Cu and Ag as realizations of simple physical models. [S0034-6861(97)00301-2] ogy,

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Section: B Helsinki Cryostatmentioning

confidence: 99%

Nuclear magnetic ordering in simple metals at positive and negative nanokelvin temperatures

1997

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“…This wire was chosen because its spin-lattice relaxation time had previously been studied down to millikelvin temperatures. 18 At their upper ends the wires were welded together and connected directly to the first nuclear stage, without any heat switch. Therefore, thermal contact between the conduction electrons in the two nuclear stages is good.…”

Section: Cryogenic Systemmentioning

confidence: 99%

“…Therefore, the theoretical interpretation of the data in Ref. 18 on fast cross-relaxation of the isotopic magnetization in a field of 7 mT should be modified. In that paper the cross-relaxation was related to rz/rD, yielding the puzzling result 80 for this ratio.…”

Section: Relaxation Of the Spin Systemmentioning

confidence: 99%

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

et al. 1980

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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.

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“…Cu-Mn) was studied quite extensively, both theoretically [85][86][87][88][89][90][91][92][93] and experimentally. [94][95][96][97][98][99][100][101][102][103][104][105][106][107][108][109][110] . The description of spin relaxation in dilute alloys has certain specific features as compared with the homogeneous systems.…”

Section: Host Nuclear Spin Diffusion In Dilute Alloysmentioning

confidence: 99%

Statistical Theory of Spin Relaxation and Diffusion in Solids

Kuzemsky

2006

J Low Temp Phys

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A comprehensive theoretical description is given for the spin relaxation and diffusion in solids. The formulation is made in a general statistical-mechanical way. The method of the nonequilibrium statistical operator (NSO) developed by Zubarev is employed to analyze a relaxation dynamics of a spin subsystem. Perturbation of this subsystem in solids may produce a nonequilibrium state which is then relaxed to an equilibrium state due to the interaction between the particles or with a thermal bath (lattice). The generalized kinetic equations were derived previously for a system weakly coupled to a thermal bath to elucidate the nature of transport and relaxation processes. In this paper, these results are used to describe the relaxation and diffusion of nuclear spins in solids. The aim is to formulate a successive and coherent microscopic description of the nuclear magnetic relaxation and diffusion in solids. The nuclear spin-lattice relaxation is considered and the Gorter relation is derived. As an example, a theory of spin diffusion of the nuclear magnetic moment in dilute alloys (like Cu-Mn) is developed.It is shown that due to the dipolar interaction between host nuclear spins and impurity spins, a nonuniform distribution in the host nuclear spin system will occur and consequently the macroscopic relaxation time will be strongly determined by the spin diffusion. The explicit expressions for the relaxation time in certain physically relevant cases are given.

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Nuclear spin-lattice relaxation of the Zeeman and the spin-spin systems in copper between 1 and 17 mK

Cited by 4 publications

References 6 publications

Nuclear magnetic ordering in simple metals at positive and negative nanokelvin temperatures

Nuclear magnetic ordering in simple metals at positive and negative nanokelvin temperatures

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

Statistical Theory of Spin Relaxation and Diffusion in Solids

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