SEM micrograph of the microlab for investigation of nanowires. The Ni-NW with in-situ prepared ohmic Au-caps has a diameter of 70 nm and a length of 18 μm. The leads R1 (hot electrode) and R2 (cold electrode) are used for the determination of the Seebeck coefficient and the resistance of the NW in four-point geometry. The temperature of the NW-caps is determined from the measured functions R1 (T) and R2 (T). The lead Ro is used as heater electrode. The magnetic field is applied perpendicular to the nanowire. The inset (grey background) shows the measurement circuit between R1 and R2 for measuring of S.
(a) Plot of thermovoltage as a function of time after switching on or off of the heating power: squares (black): Iheat = 12 mA; circle (red): Iheat = 0 mA; UTh (12 mA) = (12.395 ± 0.005) μV. A heater current of 12mA corresponds to a temperature difference δT = 0.64 K between hot and cold electrodes; t = 0 corresponds to switch on and switch off of heater current. (b) Thermovoltage as function of the heating power.
(a) Temperature increase of the ends of the nanowire as a function of the heating power at RT; squares (red): hot electrode; circles (black): cool electrode; δT-temperature difference between both electrodes. (b) Determination of the Seebeck coefficient from the slope of the measured Uth vs. δT and To = 295 K.
(a) Transversal magnetothermopower of Ni-nanowire (Iheat = 12 mA); inset of (a): Thermopower as a function of δT for different magnetic fields at RT (upper line: B = 0 T; lower line: B = 0.5 T). (b) Anisotropic magnetoresistance versus transversal magnetic field at RT; Imeas = 5 μA; the switching field is observed near 140 mT.
MTP versus AMR at RT; δT = 0.64 K; Per data point, the magnetic field varies between 0 and 0.6 T in steps of 35 mT.
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