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

Abstract

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.

The surface-to-volume ratio: a key parameter in the thermoelectric transport of topological insulator Bi2Se3nanowires

“…Further details of TE measurement can be found elsewhere. 39 To confirm the existence of TISS in our NWs, we conducted low-temperature magnetotransport measurements with a 4point contact configuration in a magnetic field (± 9 T) at 2 K in a cryogenic chamber (PPMS Dynacool, Quantum design). The 4-point device is shown as an inset of Figure 2 (a).…”

Tailoring magnetic properties in arrays of pulse-electrodeposited Co nanowires: The role of Cu additive

“…So far, single element, binary alloy, ternary alloy and multilayered magnetic NWs such as Co, Ni, Fe, NiCu, FeCo, CoCu, CoNi, FeCoCu and CoNi/Cu have been prepared using the electrodeposition technique [12][13][14][15][16][17][18][19][20]. Having paid particular attention to both the binary alloy and multilayered NWs due their potential application in the magnetoresistive and thermoelectric devices at the nanoscale, they show considerable amounts of magnetoresistance and magnetothermopower, which in turn, can compete with those of the conventional counterpart materials [18,20,21].…”

Tunable High-Field Magnetization in Strongly Exchange-Coupled Freestanding Co/CoO Core/Shell Coaxial Nanowires

“…19,21,23,25,73 Namely, the magnetic behavior is mainly dominated by the shape and magnetocrystalline anisotropies of Co, where the c-axis lies along the wire. Thus, when measuring along the wire, high coercivity (μ ∥ ≈ 150 mT) and square-type loops are obtained (i.e., easy axis behavior), while when measuring perpendicular to the wires a sheared loop with much smaller coercivity (μ ⊥ ≈ 60 mT) is observed, characteristic of a hard axis (see Fig.…”

“…19,21,23,25 Due to the random in-plane distribution of the wires, the net effect of dipolar interactions should be practically negligible so we do not expect these to significantly affect the out-of-plane magnetic behavior of our system. Remarkably, no loop shift is observed in the embedded wires after FC, indicating the absence of any significant oxidation of the wires.…”