Introduction to PAC/PAD

Mahnke, H.‐E.

doi:10.1007/bf02405137

Cited by 50 publications

(23 citation statements)

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“…Further details on TDPAD experiments can be found elsewhere. [18][19][20] Complementing the experimental measurements, we have performed first principle electronic structure calculations to examine the magnetic moment and hyperfine field of an Fe impurity embedded in the semiconductor hosts studied here. The calculations were performed within density functional theory, 22-24 using the augmented plane waves þ local orbitals (APW þ lo) method [24][25][26] as implemented in the WIEN2k package 27 to solve the scalar relativistic Kohn-Sham equations.…”

Section: Rðtþ ¼mentioning

confidence: 99%

“…[18][19][20] The nuclear spins of the probes, thus produced, are aligned perpendicular to the beam direction and therefore yield anisotropic distribution of the decaying c-radiation. In the presence of extranuclear field, e.g., internal or external magnetic field, due to hyperfine interaction, the nuclear spin precesses with Larmor frequency x L , which in turn causes time dependent modulation of the c-ray intensity.…”

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confidence: 99%

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Lattice location and local magnetism of recoil implanted Fe impurities in wide and narrow band semiconductors CdTe, CdSe, and InSb: Experiment and theory

Mohanta

Mishra

2014

Journal of Applied Physics

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Section: Rðtþ ¼mentioning

confidence: 99%

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confidence: 99%

Lattice location and local magnetism of recoil implanted Fe impurities in wide and narrow band semiconductors CdTe, CdSe, and InSb: Experiment and theory

Mohanta

Mishra

2014

Journal of Applied Physics

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“…Spin rotation spectra, R(t) were recorded in the temperature range 10 to 300 K by applying magnetic field of 2 T. Further details on the experimental method can be found in Ref. [5]. Measurements were performed in fcc and hcp Yb.…”

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confidence: 99%

“…The spectra show superposition of three frequency components arising from Mo atoms at different lattice sites. They were fitted by the function [5]: R(t) = i A i exp(−t/τ Ni )sin[2(ω Li t − θ)] to extract the amplitude A, Larmor frequency ω L and the nuclear spin relaxation time τ N of each component. Fig.2 shows the local susceptibilities,…”

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Local Magnetism of Isolated Mo Atoms at Substitutional and Interstitial Sites in Yb Metal: Experiment and Theory

Tulapurkar¹,

Mishra²,

Pillay³

et al. 2000

Phys. Rev. Lett.

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Using TDPAD experiment and local spin density calculations, we have observed large 4d moments on isolated Mo atoms at substitutional and octahedral interstitial lattice sites in Yb metal, showing Curie-Weiss local susceptibility and Korringa like spin relaxation rate. As a surprising feature, despite strong hybridization with the Yb neighbours, interstitial Mo atoms show high moment stability with small Kondo temperature. While, magnetism of Mo, at substitutional site is consistent with Kondo type antiferromagnetic d-sp exchange interaction, we suggest that moment stability at the interstitial site is strongly influenced by ferromagnetic polarization of Yb-4f5d band electrons. 74.72.Ny, 71.28.+d, 75.20.Hr, 76.80.+y The formation and stability of local magnetic moments on d-impurities in metallic hosts has been a topic of intense experimental and theoretical investigations over the past several years. While extensive studies have been made for several 3d impurities [1,2], much less information is available on the magnetism of 4d atoms in metals. In general, the d-electrons in 4d metals are regarded as being itinerant and do not show tendency towards local moment formation. Recently, applying time differential perturbed angular distribution/correlation (TD-PAD/TDPAC) methods, strong magnetic behaviour has been observed for some substitutional 4d impurities in few metals and alloys [2,3]. The results revealed that, similar to the behaviour observed for 3d impurities, magnetism of 4d ions in metals strongly depends on the type of conduction electrons in the host. Furthermore, it has been argued that moment stability measured by the Kondo temperature, T K is strongly influenced by induced spin polarization of host band electrons.In view of these aspects of magnetism for substitutional 3d and 4d impurities in metals, one can ask : can local moment occur on 3d/4d atoms at interstitial lattice sites also? If so, how stable are the moments? What is the magnitude and sign of host spin polarization and how does it influence the impurity magnetism? Intuitively, due to reduced interatomic distances and the consequent increase in the hybridization strength, one would expect suppressed magnetism for d atoms at interstitial lattice sites. However, large 3d moment has recently been observed for Fe at interstitial sites in fcc Yb metal [4]. Hitherto, magnetism of 4d atoms at interstitial lattice sites in a metal has not been investigated. In this letter we report experimental and theoretical studies on the magnetism of isolated Mo impurity atoms at substitutional and interstitial lattice sites in Yb metal. The results, obtained from TDPAD measurements and local spin density (LSD) calculations show that Mo atoms occupying substitutional and octahedral interstitial sites posses large stable 4d moments with rather small T K values. We show that lattice site dependent magnetism of Mo, especially the moment stability, is strongly influenced by the sign and strength of host conduction electron spin polarization.TDPAD experiments wer...

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“…The angular correlation is disturbed if electric field gradients (EFG) act on Q or magnetic hyperfine fields ͑B hf ͒ on m [10]. These static hyperfine interactions lead to an oscillating perturbation [11]. In the case of a static B hf , the time dependent count rates C͑t͒ are modulated involving the Larmor frequency v L g N m N B hf ͞h; no external magnetic fields were applied in our experiments.…”

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New Approach for Range Measurements of Induced Magnetic Interactions in Pd

et al. 1997

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Induced long-range magnetic interactions in Pd single crystals covered with ferromagnetic Ni are observed in perturbed angular correlation measurements applying monolayer-resolved sample preparation. The 100 Pd͞ 100 Rh probes sense magnetic interactions even seven atomic layers away from the Ni-Pd interface. The results are interpreted assuming fluctuations of magnetic moments strongly interacting with the 100 Rh nuclei. [S0031-9007(96) PACS numbers: 75.30. Hx, 75.70.Cn, 76.80.+y The range of the magnetic polarization in the strongly exchange enhanced metal Pd in contact with Ni was investigated in a pioneering magnetometry experiment as early as 1984 [1]. As the most probable interpretation, the authors attributed the additional magnetic moment to Pd, although they could not decide from the bare experimental results whether it is actually located in Ni or Pd. Meanwhile, the existence of ferromagnetic polarization in magnetic-layer systems with only a few monolayers (ML) Pd deposited on ferromagnetic substrates (Fe, Co, Ni) is experimentally well established and theoretically treated [2]. The lattice parameters of such ultrathin Pd layers differ from the bulk value as a consequence of epitaxial growth. This can influence the magnetic properties considerably [2,3]. When the surface of Pd with bulk lattice parameters, e.g., of a single crystal, is covered with a film of a ferromagnetic material (Fe, Co, Ni), neither the nature (static or fluctuating moments) nor the range of induced magnetic interactions are well known from experiments, since such a system is hardly accessible to many conventional experimental methods. Ab initio theoretical treatments of such systems are available, however [4].The present experiment offers a new approach for range measurements of induced magnetic spin polarization in Pd. The further aim is to determine the nature of the polarization in Pd with minimized disturbance of the lattice parameters. Ideally, the only wanted disturbance is the magnetic influence by the ferromagnetic coverage; we have chosen isoelectric Ni. For a quantitative range measurement preferentially a monolayer-resolving method has to be applied. For this purpose the perturbed angular correlation (PAC) method with radioactive 111 Cd probe nuclei has recently been introduced [5]. We have selected 100 Pd decaying to 100 Rh as probe nuclei. The clean preparation and controlled deposition of radioactive 100 Pd probe atoms on Pd surfaces (avoiding other contaminations) were achieved within the present experiment [6]. Thus another transition-element probe (besides the Mössbauer probe 57 Fe) is available for microscopic investigations of magnetic multilayer systems. 100 Pd͞ 100 Rh as a PAC probe is of special importance, because it can be used as an extremely diluted impurity as well as a self atom. This opens the field for local investigations of surfaces and interfaces of 4d elements or of composite 3d͞4d-element multilayers.In short the experiment is described as follows: 100 Pd atoms (10 23 10 24 of a ML) were de...

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Introduction to PAC/PAD

Cited by 50 publications

References 31 publications

Lattice location and local magnetism of recoil implanted Fe impurities in wide and narrow band semiconductors CdTe, CdSe, and InSb: Experiment and theory

Lattice location and local magnetism of recoil implanted Fe impurities in wide and narrow band semiconductors CdTe, CdSe, and InSb: Experiment and theory

Local Magnetism of Isolated Mo Atoms at Substitutional and Interstitial Sites in Yb Metal: Experiment and Theory

New Approach for Range Measurements of Induced Magnetic Interactions in Pd

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