Nuclear Electric Quadrupole Interaction of Iridium Nuclei in Dilute Alloys of Iron and Nickel

Aiga, M.; Itoh, Junkichi

doi:10.1143/jpsj.31.1844

Cited by 44 publications

(20 citation statements)

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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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confidence: 99%

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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confidence: 99%

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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“…According to Eq. ͑1͒ the resonance frequency of the NMR transition between the sublevels ͉m͘ and ͉mϩ1͘ is given by m→mϩ1 ϭ m ϩ⌬ Q ͑ mϩ 1 2 ͒, ͑2͒ m ϭ͉g N B/h͉, ͑3͒…”

Section: A Hyperfine Interaction In Cubic Fe Co and Nimentioning

confidence: 99%

“…[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. The main problem was that the quadrupole splitting of the nuclear magnetic resonance due to the SO-EFG is in most cases concealed by a much larger inhomogeneous broadening of the resonance.…”

Section: Introductionmentioning

confidence: 99%

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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“…14 Using this approximation the orbital moment and the SO-EFG can be expressed in terms of the SOC strength, the density of states at the Fermi energy, and the derivative of the density of states at the Fermi energy. This model was extended by Gehring and Williams by the introduction of the crystal potential to treat a possible dependence on the direction of the magnetization.…”

Section: Introductionmentioning

confidence: 99%

Spin-orbit induced noncubic charge distribution in cubic ferromagnets. II. Tight-binding analysis

2002

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The orbital moment and the noncubic charge distribution in ferromagnetic transition metals with cubic lattice symmetry are investigated within the tight-binding model. By combining the tight-binding approximation, perturbation theory, and the Green's function formalism for impurity scattering, approximate expressions for both effects are derived that depend only on the spin-orbit coupling strength and the density of states of the system without spin-orbit coupling. The basic relations between the orbital moment, the noncubic charge distribution, and the band structure are derived from the form of these expressions and from their application to various model band structures: We explain in this way the scaling with the spin-orbit coupling strength and bandwidth, the typical order of magnitude, the variation as a function of the band filling, the sensitivity to band structure details, and the role of the splitting between spin-up and spin-down states. For the noncubic charge distribution we derive the form of the dependence on the direction of the magnetization and show how the sign and magnitude of this anisotropy are related to the different energy distributions of e g and t 2g states. This tight-binding analysis is finally applied to the 5d impurities in Fe. The local densities of states without spin-orbit coupling are obtained by self-consistent augmented plane-wave calculations using a supercell method. The special features of the 5d impurities in Fe with respect to the band structure, the orbital moment, and the noncubic charge distribution are discussed. The general trend of the systematics is interpreted as a band filling effect. The prevailing sign of the anisotropy is ascribed to the concentration of the e g states near the Fermi energy. The results of the tight-binding analysis are compared with the experiment and a more rigorous calculation.

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Nuclear Electric Quadrupole Interaction of Iridium Nuclei in Dilute Alloys of Iron and Nickel

Cited by 44 publications

References 1 publication

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

Spin-orbit induced noncubic charge distribution in cubic ferromagnets. II. Tight-binding analysis

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