Knight Shifts of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="normal">C</mml:mi></mml:mrow><mml:mrow><mml:mn>13</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>in the Carbides of Uranium and Thorium

Lewis, W. B.; Rabideau, Sherman W.; Krikorian, N. H.; Witteman, W. G.

doi:10.1103/physrev.170.455

Cited by 42 publications

(10 citation statements)

References 51 publications

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“…Indeed, assuming a 5f 3 ( 4 I 9/2 ) electronic configuration for the U ions, and C 3 site symmetry, Burton Lewis et al found a value of μ eff = 2.3μ B . 34 However, the information provided by a Curie-Weiss fit on a polycrystalline sample of anisotropic compound is limited, and we will not further comments on these results. With decreasing temperature, the susceptibility curve goes through a broad maximum at T * ∼ 59 K. In the temperature range from about 20 to 100 K, as shown in the lower inset of Fig.…”

Section: Resultsmentioning

confidence: 98%

Evidence for persistent spin fluctuations in uranium sesquicarbide

et al. 2013

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The low-temperature magnetic susceptibility, heat capacity, and electrical resistivity of uranium sesquicarbide have been determined down to 2 K by combining measurements carried out on samples of U 2 C 3 , containing UC as minority phase, and on pure UC specimens. The presence of spin fluctuations with characteristic temperature T SF = 7 K is revealed by a nonanalytic contribution to the specific heat behaving (well below T SF ) as T 3 ln(T /T SF ), and confirmed by a T 2 increase of the electrical resistivity and a 1 − κT 2 decrease of the low-temperature magnetic susceptibility. The analysis of the specific-heat data above T SF provides a Debye temperature D ≈ 256 K and a moderate high value of the Sommerfeld coefficient, γ ≈ 42 mJ mol −1 U K −2 . The zero-temperature many-body enhancement of the electron mass is found to be m * /m ≈ 2.7. Our data rule out the occurrence of magnetic ordering in U 2 C 3 . First-principles electronic structure calculations support the absence of a magnetically ordered ground state but suggest that dynamical spin fluctuations are responsible for the electron mass enhancement.

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Section: Resultsmentioning

confidence: 98%

Evidence for persistent spin fluctuations in uranium sesquicarbide

et al. 2013

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“…This treatment takes account directly of the properties of the mirrors and was discussed by deLang. 1 Other authors [2][3][4][5][6][7][8][9][10][11] …”

Section: Discussionmentioning

confidence: 99%

“…recently on 31 P in uranium phosphides, 4-8 on 14 N in uranium mononitride, 9 and on 13 C in uranium carbides. 10 Very few spin-lattice relaxation time results have been reported for nuclei in the paramagnetic state of solids that have ordered states. Only one report can be found on T\ measurements in the paramagnetic state of uranium compounds, namely, the proton spin-lattice relaxation times in the paramagnetic state of 0-UH 3 .…”

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confidence: 99%

Nuclear Magnetic Relaxation ofP31in Diamagnetic ThP and the Paramagnetic State of UP

Kuznietz

Matzkanin

1969

Phys. Rev.

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“…11 In order to record the 14 N signals in UN, large (40-Hz) field modulations (with peak-to-peak amplitudes up to 9 Oe) were used, and signals were detected only in the dispersion mode and only by applying rf fields as high as 0.3 Oe. The same experimental conditions were used by Lewis et aL 10 in their recent NMR measurements of 13 C in uranium carbides.…”

Section: Methodsmentioning

confidence: 99%

NMR ofN14in the Paramagnetic State of Uranium Mononitride

Kuznietz

1969

Phys. Rev.

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Uranium mononitride (UN) has the NaCl-type structure, is a good conductor of electricity, is antiferromagnetic (type I) below ^53 °K, and obeys the Curie-Weiss law in the paramagnetic state in the temperature range 77-300°K. A continuous-wave NMR study was carried out on 14 N in this temperature range and in applied magnetic fields of 6340-13 000 Oe by the use of a Varian V-4210A spectrometer. The NMR signals were detected only in the dispersion mode and only by using high modulations and rf fields. The positive temperature-dependent Knight shift can be represented by K=Ko+axM, where KQ--(31.5±3.5) X10~4 is different from the Knight shift, + (10.7±1.5) X10~4, of 14 N in isostructural ThN. The difference is probably due to some temperature-independent susceptibility of ^10~3 cgs. The coefficient a is 4.20+0.25 (when XM is in cgs units), which is practically the same value as a for other uranium compounds; a is analyzed on the assumption of U +4 ions (5/ 2 configuration) and the recent value of 0.876 conduction electrons per uranium atom. In the model with uniform conduction-electron polarization, an exchange constant J s f of -(1.0=1=0.2) eV is obtained that has the same sign as in the lanthanides, but is about one order of magnitude larger; the variation is probably due to the larger extent of the 5/ electronic functions. In the Ruderman-Kittel-Kasuya-Yosida (RKKY) model, the s-f coupling constant V = -460 eV A 3 is again negative, but is about eight times higher than |r| obtained from the paramagnetic Curie temperature (6C^L-320°K) and the magnetic contribution to the resistivity. The variation of V is mainly due to the sensitivity of the RKKY sums, but also may be due to the simple RKKY model used. The constant value of a in uranium compounds, which have an ordered magnetic state, is an indication of the nonapplicability of the RKKY model to the analysis of the Knight shifts. The linewidth of 14 N in UN depends on the temperature and magnetic field. The linewidth is analyzed in terms of a constant quadrupole interaction (similar to that which contributes to the total linewidth in ThN) and a magnetic contribution that is proportional to HQ/ (T-6) (similar to that in UP with the quadrupole contribution absent). These results are compared with those on 14 N in lanthanide nitrides and with uranium compounds that have an ordered state.

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Knight Shifts ofC13in the Carbides of Uranium and Thorium

Cited by 42 publications

References 51 publications

Evidence for persistent spin fluctuations in uranium sesquicarbide

Evidence for persistent spin fluctuations in uranium sesquicarbide

Nuclear Magnetic Relaxation ofP31in Diamagnetic ThP and the Paramagnetic State of UP

NMR ofN14in the Paramagnetic State of Uranium Mononitride

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