PAC Probes as Diffusion Tracers in Solids

Collins, Gary S.; Favrot, AurE ́lie; Li, Kang; Nieuwenhuis, Egbert R.; Solodovnikov, D.; Wang, Jipeng; Zacate, Matthew O.

doi:10.1007/s10751-005-9073-8

Cited by 22 publications

(32 citation statements)

References 13 publications

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“…The jump frequencies in RIn 3 were found to depend sensitively on small deviations from the stoichiometric composition. [26][27][28] Slight composition differences are possibly responsible for the difference of the jump frequencies in RAl 3 , R = Tm, Lu and R = Yb.…”

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Electric field gradients in the rare earth–aluminium compoundsRAl2andRAl3studied by
Forker
¹
,
Presa
²

2007
Phys. Rev. B

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Perturbed angular correlation ͑PAC͒ spectroscopy has been used to investigate the electric field gradient ͑EFG͒ at the probe nucleus 111 In/ 111Cd in the paramagnetic phase of the rare earth ͑R͒-aluminium compounds RAl 2 for all R elements and Y and in RAl 3 for R = Gd, Tm, Yb, Lu. The nuclear electric quadrupole interaction ͑QI͒ between the EFG and the 111 Cd quadrupole moment was measured as a function of temperature in the range T C Ͻ T ഛ 1200 K. In the second half of the RAl 2 series and in the RAl 3 compounds, except for YbAl 3 , the quadrupole frequency q shows the monotonous decrease with increasing temperature normally observed with closed-shell probe nuclei in metallic systems. In the early members of the RAl 2 series, however, q ͑T͒ passes through a maximum at T ϳ 300 K. It is proposed that this unusual behavior reflects a contribution of the 4f shell of the R constituents to the EFG at the Al site which is quenched at higher temperatures by thermal averaging of the 4f quadrupole moment. In the intermediate-valence compound YbAl 3 the temperature dependence of the QI exhibits a shallow maximum which can be related to the temperature variation of the 4f hole occupation. Furthermore the PAC spectra provide information on the site preference of the Cd. The temperature dependence of the relaxation rates shows an Arrhenius behavior with jump activation enthalpies E A = 1.6͑1͒ eV for R = Tm, Lu and E A = 1.2͑1͒ eV for R =Yb.

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confidence: 99%

Electric field gradients in the rare earth–aluminium compoundsRAl2andRAl3studied by
Forker
¹
,
Presa
²

2007
Phys. Rev. B

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“…Such jumps produce decoherence of nuclear quadrupole precessions that is exhibited as "damping" in time-domain PAC perturbation functions [1]. In good approximation, as shown in [2], the damping time is equal to the mean residence time of a probe atom on a site, or inverse of the total jump frequency w. For cubic compounds, w is related to the diffusivity D via 6…”

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Diffusion in Binary and Pseudo-Binary L1<sub>2</sub> Indides, Stannides, Gallides and Aluminides of Rare-Earth Elements as Studied Using Perturbed Angular Correlation of <sup>111</sup>In/Cd

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Collins

2012

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Diffusional jumps can produce fluctuating electric field gradients at nuclei of jumping atoms. Using perturbed angular correlation of gamma rays (PAC), jumps of probe atoms cause nuclear quadrupole relaxation that can be fitted to obtain the mean jump frequency. An overview is given of the application of this approach to highly ordered intermetallic compounds having the L1 2 (Cu 3 Au) crystal structure. New results are then presented for jump frequencies of 111 In/Cd probe atoms in pseudo-binary L1 2 compounds of the forms In 3 (La 1-x Pr x ) and (In 1-x Sn x ) 3 La. For the mixed rare-earth system, jump frequencies are found to scale with composition between jump frequencies of the end-member phases In 3 La and In 3 Pr. However, for the mixed sp-element system, a large decrease in jump frequency is observed as Sn atoms substitute for In-atoms. This difference in behavior appears to depend on whether atomic disorder is on the diffusion sublattice (In-Sn substitution), as opposed to a neighboring sublattice (La-Pr substitution), whether or not there is a difference in diffusion mechanism between end-member phases, and/or whether or not there is a valence difference between the mixing atoms. All three conditions apply for only (In 1-x Sn x ) 3 La.

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“…2 shows that relaxation frequencies for the two samples are indistinguishable within the precision of measurement. This is a surprise since large differences have been observed for other "line compounds" such as for In 3 R phases having the L1 2 structure (R = rare earth) [4,5]. 3.…”

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Diffusion of 111Cd probes in Ga7Pt3 studied via nuclear quadrupole relaxation

2007

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Diffusion of 111 In/Cd impurity atoms was studied in Ga 7 Pt 3 at the atomic level using the method of perturbed angular correlation of gamma rays (PAC). As in previous measurements on Ga 7 Pd 3 , probes were observed to occupy two inequivalent Ga-sublattices. Quadrupole interaction perturbation functions for each site exhibited damping at elevated temperatures that is attributed to nuclear relaxation caused by stochastic jumps of the probe atoms accompanied by reorientation of axes of the electric field gradient tensor. Fitted relaxation frequencies, proportional to mean jump frequencies of the probe, were thermally activated. Arrhenius plots revealed jump-frequency activation enthalpies of 0.94 (8) and 0.67 (4) eV for the two sites and frequency prefactors close to 1 THz. Results were similar to those found previously for Ga 7 Pd 3 , although jump frequencies are about 100 times lower in Ga 7 Pt 3 .

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PAC Probes as Diffusion Tracers in Solids

Cited by 22 publications

References 13 publications

Electric field gradients in the rare earth–aluminium compoundsRAl2andRAl3studied by
Forker
¹
,
Presa
²

2007
Phys. Rev. B

Electric field gradients in the rare earth–aluminium compoundsRAl2andRAl3studied by
Forker
¹
,
Presa
²

2007
Phys. Rev. B

Diffusion in Binary and Pseudo-Binary L1<sub>2</sub> Indides, Stannides, Gallides and Aluminides of Rare-Earth Elements as Studied Using Perturbed Angular Correlation of <sup>111</sup>In/Cd

Diffusion of 111Cd probes in Ga7Pt3 studied via nuclear quadrupole relaxation

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PAC Probes as Diffusion Tracers in Solids

Cited by 22 publications

References 13 publications

Electric field gradients in the rare earth–aluminium compoundsRAl2andRAl3studied byForker1, Presa2 2007Phys. Rev. B

Electric field gradients in the rare earth–aluminium compoundsRAl2andRAl3studied byForker1, Presa2 2007Phys. Rev. B

Diffusion in Binary and Pseudo-Binary L1<sub>2</sub> Indides, Stannides, Gallides and Aluminides of Rare-Earth Elements as Studied Using Perturbed Angular Correlation of <sup>111</sup>In/Cd

Diffusion of 111Cd probes in Ga7Pt3 studied via nuclear quadrupole relaxation

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Electric field gradients in the rare earth–aluminium compoundsRAl2andRAl3studied by
Forker
¹
,
Presa
²

2007
Phys. Rev. B

Electric field gradients in the rare earth–aluminium compoundsRAl2andRAl3studied by
Forker
¹
,
Presa
²

2007
Phys. Rev. B