The thermoelectric power of dilute gold-iron alloys

Berman, R.; Kopp, J.

doi:10.1088/0305-4608/1/4/318

Cited by 42 publications

(10 citation statements)

References 22 publications

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“…The reduction in thermopower is as high as 20% in a 13 T field. The shape of the ∆S(H) vs H curves also indicates that the change is steeper at intermediate fields followed by a tendency for saturation at higher fields, which has been seen earlier also in Kondo systems and magnetic alloys [28,29]. This is indicative of a field induced ordering of spins in the system and consequent suppression of spin entropy transport.…”

Section: (B) Are Fits To Eq (3)supporting

confidence: 61%

“…In Kondo systems, the entropy carried by the spin degree of freedom is expected to be suppressed by an external magnetic field, and therefore, the S(T) should show magnetic field effects in the Kondo regime. Some early measurements on gold alloys show large suppression of thermopower by a magnetic field [28,29]. Clearly, measurements of thermopower and its magnetic field dependence in LAO/STO type 2DEG system can provide important clue for the origin of resistivity minimum and magnetic correlations.…”

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confidence: 99%

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Magnetothermopower ofδ-dopedLaTiO3/SrTiO3interfaces in the Kondo regime

et al. 2014

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Measurements of magneto-thermopower (S(H, T)) of interfacial delta doped LaTiO3/SrTiO3 (LTO/STO) heterostructure by an iso-structural antiferromagnetic perovskite LaCrO3 are reported. The thermoelectric power of the pure LTO/STO interface at 300 K is ≈ 118 µV/K, but increases dramatically on δ-doping. The observed linear temperature dependence of S(T) over the temperature range 100 K to 300 K is in agreement with the theory of diffusion thermopower of a two-dimensional electron gas. The S(T) displays a distinct enhancement in the temperature range (T < 100 K) where the sheet resistance shows a Kondo-type minimum. We attributed this maximum in S(T) to Kondo scattering of conduction electron by localized impurity spins at the interface. The suppression of S by a magnetic field, and the isotropic nature of the suppression in out-of-plane and in-plane field geometries further strengthen the Kondo model based interpretation of S(H, T).

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Section: (B) Are Fits To Eq (3)supporting

confidence: 61%

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confidence: 99%

Magnetothermopower ofδ-dopedLaTiO3/SrTiO3interfaces in the Kondo regime

et al. 2014

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“…However, an extremely rough estimate of the level of impurities can be made either by determining the impurity electron mean free path and assuming unity probability of the electron-impurity scattering or by simply comparing to literature estimates of the specific impurity resistance 74 . These suggest that Au resistivities as high as shown here could result from between ∼ 500 ppm and ∼ 1% impurity content.…”

Section: A Quantification and Comparison Of G ↑↓ Eff And α Shmentioning

confidence: 99%

Efficient spin transport through native oxides of nickel and permalloy with platinum and gold overlayers

et al. 2016

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We present measurements of spin pumping detected by the inverse spin Hall effect voltage and ferromagnetic resonance spectroscopy in a series of metallic ferromagnet/normal metal thin film stacks. We compare heterostructures grown in situ to those where either a magnetic or nonmagnetic oxide is introduced between the two metals. The heterostructures, either nickel with a platinum overlayer (Ni/Pt) or the nickel-iron alloy permalloy (Py) with a gold overlayer (Py/Au), were also characterized in detail using grazing-incidence X-ray reflectivity, Auger electron spectroscopy, and both SQUID and alternating-gradient magnetometry. We verify the presence of oxide layers, characterize layer thickness, composition, and roughness, and probe saturation magnetization, coercivity, and anisotropy. The results show that while the presence of a non-magnetic oxide at the interface suppresses spin transport from the ferromagnet to the non-magnetic metal, a thin magnetic oxide (here the native oxide formed on both Py and Ni) somewhat enhances the product of the spin mixing conductance and the spin Hall angle. We also observe clear evidence of an out-of-plane component of magnetic anisotropy in Ni/Pt samples that is enhanced in the presence of the native oxide, resulting in perpendicular exchange bias. Finally, the dc inverse spinHall voltages generated at ferromagnetic resonance in our Py/Au samples are large, and suggest values for the spin Hall angle in gold of 0.04 < α SH < 0.22, in line with the highest values reported for Au. This is interpreted as resulting from Fe impurities. We present indirect evidence that the Au films described here indeed have significant impurity levels.2

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“…21 These spin-dependent scattering channels can account for a large fraction of the total scattering rate, as is demonstrated by the large, negative "anomalous" magnetoresistance of dilute alloys such as Au(Fe), which results from the "freezing out" of spin-flip processes at low temperatures and in strong magnetic fields. 22 The presence of spin-dependent scattering (SDS) corresponds to unequal broadening of the up-spin and down-spin Landau levels ( Fig. 1) and to different dHvA Dingle temperatures for spin-up and spin-down electrons on the same extremal Fermi surface orbit:…”

Section: Exchange Energy Shitt and Spin-dependent Scatteringmentioning

confidence: 99%

“…(1) or (19)]. The reason for this is that the driving field for the quantum oscillations is the magnetic induction, B = H+4~(1-N.)b~ r (22) rather than the applied field H. Here N, is the "effective" demagnetizing factor for the dHvA sample. * When Eq.…”

Section: The General Case: Magnetic Interaction (Mi) Effect Harmonic mentioning

confidence: 99%

Electronic properties from analysis of the harmonic content of the de Haas-van Alphen effect: Application to dilute magnetic alloys

1978

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A new technique, third harmonic de Haas-van Alphen (dHvA) wave shape analysis, is described for measurement of the spin-dependent interactions between conduction electrons and local moments in dilute alloys. We derive expressions for the harmonic content of the dHvA effect in a general case, including simultaneous contributions due to (1) magnetic interaction (MI or Shoenberg effect), (2) the spin-dependent scattering (SDS) of conduction electrons, and (3) exchange energy shifts in their Landau levels due to local moments, in addition to the usual Lifshitz-Kosevich harmonic content. The effects of MI and SDS mix nonlinearly in determining the observable amplitude and phase of each resultant dHvA harmonic. One important consequence of this mixing is that the observation of a spin splitting zero of the dHvA amplitude is not indicative of equal scattering rates for spin-up and spin-down electrons, in the presence of ML These techniques are then illustrated by applying them to studies of the dilute alloy systems Au(Fe ) and Au (Co), both of which are found to exhibit local magnetic moments, though apparently of quite different origin. For Au(Fe) the exchange energy shift (exchange field) and the spin-dependent scattering rates were determined as functions of (H,T). A 3:1 anisotropy of spin-up and spin-down electron scattering rates was observed for the (111) neck orbit. For Au( Co ) we report the first dHvA observations of interaction effects between impurities, via measurements of the spin-dependent scattering of conduction electrons by magnetic pairs of Co impurities. We conclude that the dHvA effect appears to be a sensitive probe for determining impurity spin behavior in a magnetic field, and for measuring cyclotron orbitally averaged values of the exchange constant Jo,bit in very dilute local moment systems. Similarly, the ability to resolve spin-dependent information allows the onset of solute interactions leading to magnetism to be observed at very low solute concentrations.Finally, the possibility of applying these same third harmonic wave shape analysis procedures for the measurement of conduction electron orbital gfactors in metals is briefly discussed, and one example of such a measurement for a Au(Ag) dilute alloy, is given

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The thermoelectric power of dilute gold-iron alloys

Cited by 42 publications

References 22 publications

Magnetothermopower ofδ-dopedLaTiO3/SrTiO3interfaces in the Kondo regime

Magnetothermopower ofδ-dopedLaTiO3/SrTiO3interfaces in the Kondo regime

Efficient spin transport through native oxides of nickel and permalloy with platinum and gold overlayers

Electronic properties from analysis of the harmonic content of the de Haas-van Alphen effect: Application to dilute magnetic alloys

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