Nuclear Gamma Resonance Study of the Ir —Fe and Ir —Ni Alloy Systems

Mößbauer, R. L.; Lengsfeld, M.; Lieres, W. Von; Potzel, W.; Teschner, T.; Wagner, F. E.; Kaindl, G.

doi:10.1515/zna-1971-0303

Cited by 33 publications

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“…The electric field gradient (EFG) at the site of impurity nuclei in cubic ferromagnetic hosts such as Fe, Ni, and fcc-Co has been the subject of many investigations, both experimental [1][2][3][4][5][6][7][8][9] and theoretical [5,10,11]. It was first observed by nuclear magnetic resonance (NMR) of 191 Ir and 193 Ir in polycrystalline dilute ferromagnetic alloys of Fe and Ni [1,5].…”

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Dependence of the Electric Field Gradient of Ir in Fe on the Direction of Magnetization with respect to the Crystallographic Axes

et al. 1997

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The electric quadrupole interaction of 188 Ir ͑I p 1 2 ; T 1͞2 41.5 h͒ in a Fe single crystal was measured for magnetization parallel to the crystallographic [100], [110], and [111] axes. Contrary to all previous experiments, a strong dependence of the electric field gradient on the direction of the magnetization with respect to the crystallographic axes was observed for the first time.[ S0031-9007(97) PACS numbers: 76.60. Jx, 75.50.Bb, 76.60.Gv, 76.80.+ y The electric field gradient (EFG) at the site of impurity nuclei in cubic ferromagnetic hosts such as Fe, Ni, and fcc-Co has been the subject of many investigations, both experimental [1-9] and theoretical [5,10,11]. It was first observed by nuclear magnetic resonance (NMR) of where eq V zz (henceforth denoted as EFG) is the principal component of the traceless EFG tensor and eQ is the nuclear spectroscopic quadrupole moment. If the EQI is collinear with the magnetic hyperfine interaction, the magnetic resonance frequency is split into a set of 2I equidistant subresonances, where I is the nuclear spin. The subresonance separation is given byThe satellite resonances were considerably broader than the central line. Mainly, the following two explanations were discussed: (i) The additional broadening is due to lattice inhomogeneities. (ii) The EFG depends on the direction of the magnetization with respect to the crystal axes. To explore whether the second possibility was the origin for this broadening, Aiga and Itoh prepared single crystal alloys of Fe-0.3% Ir by the stress annealing method. The NMR measurements yielded exactly the same spectra as observed for the polycrystal samples [5]. Thus Aiga and Itoh concluded that the quadrupole interaction is almost independent of the direction of the magnetization, and even if there is some anisotropy, it is of the order of, or less than, a few hundred kHz. Johnston and Stone performed NMR on oriented nuclei (NMR-ON) measurements on 192

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Dependence of the Electric Field Gradient of Ir in Fe on the Direction of Magnetization with respect to the Crystallographic Axes

et al. 1997

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“…It was first observed by Aiga and Itoh with nuclear magnetic resonance (NMR) measurements on 191 Ir and 193 Ir in polycrystalline Fe and Ni [1,5]. Shortly afterwards it was confirmed by Mössbauer-effect measurements on 193 Ir in Fe and Ni [2,3]. For the system AuFe the EFG could also be detected with spin echo measurements on 197 AuFe [8,9].…”

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confidence: 78%

“…

[2,3]. For the system AuFe the EFG could also be detected with spin echo measurements on 197 AuFe [8,9].

In principle, the EFG in a cubic ferromagnet can arise from magnetostriction and from unquenched local moments.

…”

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Spin-Orbit Electric Field Gradient in Cubic Ferromagnets: Strong Magnetization-Direction Dependence of the Field Gradient Distribution

et al. 1999

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[2,3]. For the system AuFe the EFG could also be detected with spin echo measurements on 197 AuFe [8,9].In principle, the EFG in a cubic ferromagnet can arise from magnetostriction and from unquenched local moments. As the observed EFG's are much larger than an EFG due to magnetostriction could be, it was early adopted that the main source is the unquenched orbital momentum [13][14][15]. From theoretical calculations Demangeat [13] postulated that EFG's originating from an unquenched orbital momentum should strongly depend on the direction of magnetization with respect to the crystallographic axes. Based on experimental results of NMR measurements on 191,193 Ir in Fe single crystals [5] and NMR on orientated nuclei (NMR-ON) measurements on 192 Ir in a Ni single crystal [4] it was concluded, however, that such a dependence does not exist. Another theoretical approach was considered by Gehring and Williams [15]. In the general framework of their model, the EFG may, depending on the relative sizes of spin-orbit coupling, the crystal field, and the exchange splitting, depend on the direction of the magnetization with respect to the crystal axes, or not. Led by the experiments suggesting the EFG to be invariant, they concluded that the effects of the crystal field can be neglected, which leads to an invariant EFG.Recent NMR-ON and modulated adiabatic fast passage on oriented nuclei (MAPON) measurements on Z 77 188 Ir in an Fe single crystal showed a strong dependence of the EFG on the direction of magnetization with respect to the crystallographic axes [11]. In these experiments no special attention was directed to the widths of the EFG distributions, as there was no theoretical hint that the EFG width could be directional dependent. The measured ratio, G ͓͑100͔͒ ͞G ͓͑111͔͒1.5͑5͒, showed, however, that the width could be larger for M k ͓100͔ than for M k ͓111͔. On the other hand, these data were not conclusive because of the too large statistical error. Thus, it was concluded that the EFG is sharp and that the distribution is introduced by the nonperfect surface quality of the used single crystal.

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“…[1][2][3][4] It was explained as a consequence of the spin-orbit coupling. 1,[5][6][7] The spin-orbit EFG ͑SO-EFG͒ was observed since then for several other impurity host combinations, [8][9][10] but precise data remained until recently restricted to only a few favorable systems.…”

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Spin-orbit induced noncubic charge distribution in cubic ferromagnets. I. Electric field gradient measurements on5dimpurities in Fe and Ni

et al. 2002

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The spin-orbit induced electric field gradient at the nuclear site of 183 Os and 183 Re impurities in Fe and of 191 Pt and 186 Ir impurities in Ni was determined for ͓100͔, ͓110͔, and ͓111͔ orientations of the magnetization. The measurements were performed on single-crystal samples using nuclear magnetic resonance on oriented nuclei and modulated adiabatic fast passage on oriented nuclei. In the Ni experiments the electric field gradient was also determined for other orientations of the magnetization in the ͑110͒ plane. These data, together with previous results on the 5d impurities, provide the first fairly complete data set on the spin-orbit induced electric field gradient in cubic Fe, Co, and Ni. Our results establish in particular that the effect depends in general considerably on the direction of the magnetization. We summarize the present knowledge of these electric field gradients, their magnitude, their systematics, and the form and magnitude of their dependence on the direction of the magnetization. The properties of the effect are explained within the tight-binding model in terms of the spin-orbit induced deformation of the electron distribution. We also present and discuss data on the dependence of the hyperfine field on the direction of the magnetization, which was found to be smaller than 10 Ϫ3 , and on the inhomogeneous broadening of the electric field gradient.

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Nuclear Gamma Resonance Study of the Ir —Fe and Ir —Ni Alloy Systems

Cited by 33 publications

References 0 publications

Dependence of the Electric Field Gradient of Ir in Fe on the Direction of Magnetization with respect to the Crystallographic Axes

Dependence of the Electric Field Gradient of Ir in Fe on the Direction of Magnetization with respect to the Crystallographic Axes

Spin-Orbit Electric Field Gradient in Cubic Ferromagnets: Strong Magnetization-Direction Dependence of the Field Gradient Distribution

Spin-orbit induced noncubic charge distribution in cubic ferromagnets. I. Electric field gradient measurements on5dimpurities in Fe and Ni

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