Transport Properties of the Ferromagnetic Metals. I. Cobalt

Laubitz, M. J.; Matsumura, T.

doi:10.1139/p73-163

Cited by 58 publications

(26 citation statements)

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“…By contrast, the present Co/Cu multilayers have an fcc structure and the lateral grain size is also definitely larger than in the previously studied electrodeposited Co since this is a prerequisite for the observation of a significant GMR. On the other hand,  0 (300 K) = 6 cm was reported for well-annealed, defect-free bulk hcp-Co by Laubitz et al 55 These latter authors have also reported data 55 from which we can see that around the temperature of the hcp-fcc transition of bulk Co (at about 700 K) the resistivity of the fcc phase is by about 8 % smaller than that of the hcp phase. By assuming an identical temperature dependence of  for both phases, we can assess  0 (300 K) = 5.5 cm for bulk fcc-Co. On the other hand, we can estimate an incremental resistivity of about 0.5 cm for the magnetic layer due to the small amount of Cu in it (this value is obtained under the plausible assumption that the resistivity increase due to alloyed Cu is the same for the Ni-Cu and the Co-Cu systems in their fcc phases and taking the incremental resistivity of Cu reported for fcc-Ni 49 ).…”

Section: A Zero-field Electrical Resistivitysupporting

confidence: 63%

Giant magnetoresistance in electrodeposited Co-Cu/Cu multilayers: Origin of the absence of oscillatory behavior

et al. 2009

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─ A detailed study of the evolution of the magnetoresistance was performed on electrodeposited Co/Cu multilayers with Cu layer thicknesses ranging from 0.5 nm to 4.5 nm. For thin Cu layers (up to 1.5 nm), anisotropic magnetoresistance (AMR) was observed whereas multilayers with thicker Cu layers exhibited clear giant magnetoresistance (GMR) behaviour. The GMR magnitude increased up to about 3.5 to 4 nm Cu layer thickness and slightly decreased afterwards. According to magnetic measurements, all samples exhibited ferromagnetic (FM) behaviour. The relative remanence turned out to be about 0.75 for both AMR and GMR type multilayers. This clearly indicates the absence of an antiferromagnetic (AF) coupling between adjacent magnetic layers for Cu layers even above 1.5 nm where the GMR effect occurs. The AMR behaviour at low spacer thicknesses indicates the presence of strong FM coupling (due to, e.g., pin-holes in the spacer and/or areas of the Cu layer where the layer thickness is very small). With increasing spacer thickness, the pin-hole density reduces and/or the layer thickness uniformity improves which both lead to a weakening of the FM coupling. This improvement in multilayer structure quality results in a better separation of magnetic layers and the weaker coupling (or complete absence of interlayer coupling) enables a more random magnetization orientation of adjacent layers, all this leading to an increase of the GMR. Coercive field and zero-field resistivity measurements as well as the results of a structural study reported earlier on the same multilayers provide independent evidence for the microstructural features established here. A critical analysis of former results on electrodeposited Co/Cu multilayers suggests the absence of an oscillating GMR in these systems. It is pointed out that the large GMR reported previously on such Co/Cu multilayers at Cu layer thicknesses around 1 nm can be attributed to the presence of a fairly large superparamagnetic (SPM) fraction rather than being due to a strong AF coupling. In the absence of SPM regions as in the present study, AMR only occurs at low spacer thicknesses due to the dominating FM coupling.

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Section: A Zero-field Electrical Resistivitysupporting

confidence: 63%

Giant magnetoresistance in electrodeposited Co-Cu/Cu multilayers: Origin of the absence of oscillatory behavior

et al. 2009

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“…3 with bulk literature thermopower values for Co 14 and Cu 15 . The Co film grown at a base pressure of 6 x 10 −10 torr has a lower resistivity and larger thermopower than the second Co film grown at a base pressure of 1 x 10 −10 .…”

Section: Resultsmentioning

confidence: 68%

Thermopower and resistivity in ferromagnetic thin films near room temperature

et al. 2011

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We present measurements of thermopower (Seebeck coefficient) and electrical resistivity of a wide selection of polycrystalline ferromagnetic films with thicknesses ranging from 60 − 167 nm. For comparison, a copper film of similar thickness was measured with the same techniques. Both the thermal and electrical measurements, made as a function of temperature from 77 − 325 Kelvin, are made using a micro-machined thermal isolation platform consisting of a suspended, patterned silicon-nitride membrane. We observe a strong correlation between the resistivity of the films and the thermopower. Films with higher resistivity and residual resistivity ratios, indicating a higher concentration of static defects such as impurities or grain boundaries, with rare exception show thermopower of the same sign, but with absolute magnitude reduced from the thermopower of the corresponding bulk material. In addition, iron films exhibit the pronounced low-temperature peak in thermopower associated with magnon drag, with a magnitude similar to that seen in bulk iron alloys. These results provide important groundwork for ongoing studies of related thermoelectric effects in nanomagnetic systems, such as the spin Seebeck effect.

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“…As explained above, the thermopower for Co/Cu and Ni/Cu multilayers is estimated from the literature values for bulk in reference to Pt 16,21,[76][77][78] . Since the composition has a stronger influence than the layer thicknesses, the Co-Ni to Cu ratio is set to 5:1.…”

Section: B Magnetothermopowermentioning

confidence: 99%

Magnetothermopower and magnetoresistance of single Co-Ni/Cu multilayered nanowires

et al. 2014

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The magnetothermopower and the magnetoresistance of single Co-Ni/Cu multilayered nanowires with various thicknesses of the Cu spacer are investigated. Both kinds of measurement have been performed as a function of temperature (50 K to 325 K) and under applied magnetic fields perpendicular to the nanowire axis, with magnitudes up to -15 % at room temperature. A linear relation between thermopower S and electrical conductivity σ of the nanowires is found, with the magnetic field as an implicit variable. Combining the linear behavior of the S vs. σ and the Mott formula, the energy derivative of the resistivity has been determined. In order to extract the true nanowire materials parameters from the measured thermopower, a simple model based on the Mott formula is employed to distinguish the individual thermopower contributions of the sample. By assuming that the non-diffusive thermopower contributions of the nanowire can be neglected, it was found that the magnetic field induced changes of thermopower and resistivity are equivalent. The emphasis in the present paper is on the comparison of the magnetoresistance and magnetothermopower results and it is found that the same correlation is valid between the two sets of data for all samples, irrespective of the relative importance of the giant magnetoresistance or anisotropic magnetoresistance contributions in the various individual nanowires.

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Transport Properties of the Ferromagnetic Metals. I. Cobalt

Cited by 58 publications

References 0 publications

Giant magnetoresistance in electrodeposited Co-Cu/Cu multilayers: Origin of the absence of oscillatory behavior

Giant magnetoresistance in electrodeposited Co-Cu/Cu multilayers: Origin of the absence of oscillatory behavior

Thermopower and resistivity in ferromagnetic thin films near room temperature

Magnetothermopower and magnetoresistance of single Co-Ni/Cu multilayered nanowires

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