Nuclear spin lattice relaxation of186ReFe and182TaFe: the role of spin wave mechanisms

Bobek, C.; Dullenbacher, R.; Klein, E.

doi:10.1007/bf02320322

Cited by 6 publications

(7 citation statements)

References 33 publications

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“…6 In this way, the magnetic-field dependence of the relaxation is attributed to the magneticfield dependence of the enhancement factor. The EFM provided a description of the field dependence of the relaxation in polycrystalline samples, 6,7 and it was consistent with the main features of the field dependence in single-crystal samples, in particular, with the occurrence of peaks for certain directions of the magnetic field. 2 However, a critical experimental test of the EFM was still missing, because in polycrystalline samples, the field dependence of the enhancement factor is not well known, and the few relaxation experiments on single-crystal samples 8,9 had not been interpreted quantitatively by the EFM.…”

Section: Introductionsupporting

confidence: 69%

“…Nevertheless, the previous interpretation of those experiments is of interest, because it seemed to support the assumption = 2: The field dependence of the relaxation could be described by the EFM and =2, if B was parametrized by B a + B ext , and B a was adjusted via least squares fit. 6,7,53,54 However, B a and are strongly correlated, and over a fairly large magnetic-field region, a wrong choice of one of those parameters can be compensated by a wrong choice of the other parameter. This was demonstrated in this work for 186 IrFe: The field dependence of R could almost equally well be described by = 1.39 and the "correct" B a or by = 2 and a "wrong," distinctly larger B a .…”

Section: Other Experimentsmentioning

confidence: 99%

“…Since the reliability of relaxation measurements by nuclear magnetic resonance on oriented nuclei ͑NMR-ON͒, the technique that was used in this work, had been questioned in the past, 3,7,14 the theory of NMR-ON was also reexamined. In particular, the practice to use transition rates to describe the effect of a coherent rf field on the sublevel populations had been doubted.…”

Section: Introductionmentioning

confidence: 99%

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Origin of the magnetic-field dependence of the nuclear spin-lattice relaxation in iron

et al. 2008

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The magnetic-field dependence of the nuclear spin-lattice relaxation at Ir impurities in Fe was measured for fields between 0 and 2 T parallel to the ͓100͔ direction. The reliability of the applied technique of nuclear magnetic resonance on oriented nuclei was demonstrated by measurements at different radio-frequency ͑rf͒ field strengths. The interpretation of the relaxation curves, which used transition rates to describe the excitation of the nuclear spins by a frequency-modulated rf field, was confirmed by model calculations. The magneticfield dependence of the so-called enhancement factor for rf fields, which is closely related to the magnetic-field dependence of the spin-lattice relaxation, was also measured. For several magnetic-field-dependent relaxation mechanisms, the form and the magnitude of the field dependence were derived. Only the relaxation via eddy-current damping and Gilbert damping could explain the observed field dependence. Using reasonable values of the damping parameters, the field dependence could perfectly be described. This relaxation mechanism is, therefore, identified as the origin of the magnetic-field dependence of the spin-lattice relaxation in Fe. The detailed theory, as well as an approximate expression, is derived, and the dependences on the wave vector, the resonance frequency, the conductivity, the temperature, and the surface conditions are discussed. The theory is related to previous attempts to understand the field dependence of the relaxation, and it is used to reinterpret previous relaxation experiments in Fe. Moreover, it is predicted that the field dependences of the relaxation in Fe and Co, on one side, and in Ni, on the other side, differ substantially, and it is suggested that the literature values of the high-field limits of the relaxation constants in Fe are slightly too large.

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Section: Introductionsupporting

confidence: 69%

Section: Other Experimentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Origin of the magnetic-field dependence of the nuclear spin-lattice relaxation in iron

et al. 2008

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“…All calculated rates are too small by a factor of 2-5. This can be interpreted as an indication that an important relaxation mechanism is missing in his model [5]. At present, however, it cannot be stated whether this missing mechanism is the relaxation via electronic spin waves.…”

mentioning

confidence: 89%

“…This increase is attributed to the interaction of 191 Pt with nuclear magnons originating from the 59 Co nuclear spin system. [ The nuclear spin-lattice relaxation (NSLR) of impurity nuclei in the ferromagnetic host lattices Fe, Co, and Ni has been the subject of many investigations, both experimental and theoretical [1][2][3][4][5][6][7][8][9][10][11]. Nevertheless, not all mechanisms which are responsible for the relaxation process are understood in detail.…”

Section: G Seewald E Hagn and E Zechmentioning

confidence: 99%

Observation of a Nuclear-Magnon Contribution to the Nuclear Spin-Lattice Relaxation ofP191tin Ferromagnetic Cobalt

1997

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We report the first indication for a nuclear spin-lattice relaxation mechanism originating from the coupling of the impurity nuclei to nuclear magnons. The magnetic hyperfine interaction and the nuclear spin-lattice relaxation of 191 Pt ͑T 1͞2 2.8 d͒ in fcc Co were measured with NMR on oriented nuclei at temperatures between 8 and 14 mK in external magnetic fields B ext 0.1 10 kG. Between B ext 5 and 1 kG the relaxation rate increases by 2 orders of magnitude. This increase is attributed to the interaction of 191 Pt with nuclear magnons originating from the 59 Co nuclear spin system. [S0031-9007(97)03473-X] PACS numbers: 76.60. Es, 75.30.Ds, 75.50.Cc, 76.80. + y The nuclear spin-lattice relaxation (NSLR) of impurity nuclei in the ferromagnetic host lattices Fe, Co, and Ni has been the subject of many investigations, both experimental and theoretical [1][2][3][4][5][6][7][8][9][10][11]. Nevertheless, not all mechanisms which are responsible for the relaxation process are understood in detail.The strength of the NSLR is described by a relaxation rate,where C K is a specific constant for each impurity-host system, analogous to the Korringa constant. At present, it is an open question whether an electronic spin-wave mechanism yields an appreciable contribution to the relaxation rate. Weger [1] studied the relaxation in Fe, Co, and Ni. He proposed that there is a strong contribution to the relaxation rate which originates from the interaction of the conduction electrons with the nuclei via electronic spin waves. Moriya [2] performed calculations including d-band electrons in a tight-binding approximation. He found that the predominant NSLR mechanism comes from the fluctuation of the orbital current of the d-band electrons and that the electronic spin-wave contribution is smaller by 1 or 2 orders of magnitude. Ab initio calculations of the NSLR rates were started by Kanamori et al. [3]. In 1988, Akai [4] published such calculations for all elements as impurities in Fe (with the exception of the rare earths and actinides), in which electronic spin-wave processes were not included. A comparison of the calculated rates with experimental rates shows a unique trend. All calculated rates are too small by a factor of 2-5. This can be interpreted as an indication that an important relaxation mechanism is missing in his model [5]. At present, however, it cannot be stated whether this missing mechanism is the relaxation via electronic spin waves. As another experimental fact, it was early found that the relaxation rate depends on the external magnetic field B ext [6-11]: For high fields ͑B ext * 6 kG͒, the relaxation rate is field independent ͑R`͒; for small fields ͑B ext & 1 kG͒, the relaxation rate increases by a factor ϳ3 10. This field dependence of the NSLR is still a controversial subject. With NMR, Kontani et al. [6] observed an increase of the NSLR rate between high field and zero field for several 3d and 4d impurities in Fe. They tried to explain this field dependence as a relaxation mechanism due to electronic spin ...

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Effect of oxidation of cobalt-based nanowires on NMR spin-lattice relaxation

2000

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Nuclear spin-lattice relaxation measurements were performed on Co-based magnetic nanowires, in zero field and in 1 T applied field. A measurement method is developped that allows a confident interpretation of the experimental data. An enhanced relaxation due to a thermally activated phenomenon associated to oxidation is reported for the first time in the nuclear magnetic resonance of ferromagnetic systems.

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Nuclear spin lattice relaxation of186ReFe and182TaFe: the role of spin wave mechanisms

Cited by 6 publications

References 33 publications

Origin of the magnetic-field dependence of the nuclear spin-lattice relaxation in iron

Origin of the magnetic-field dependence of the nuclear spin-lattice relaxation in iron

Observation of a Nuclear-Magnon Contribution to the Nuclear Spin-Lattice Relaxation ofP191tin Ferromagnetic Cobalt

Effect of oxidation of cobalt-based nanowires on NMR spin-lattice relaxation

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