Schematic representation of the inverse Wiedemann effect (IWE) exhibited by our PLD cylindrical films. (a) Whenever an ac current flows through the cylindrical substrate the sample is subjected to a circular magnetic field . An applied torque generates a helical magnetic anisotropy in the magnetostrictive sample and a variation of the longitudinal component of the magnetic flux is detected in a pickup coil. (b) Schematic representation of the system substrate film showing the direction of the magnetization of the film, , and its longitudinal component, , after the generation of a helical magnetic anisotropy. Also indicated is the direction of the applied magnetic field , as well as the thickness of the film, , deposited on the metallic wire.
Schematic representation of the experimental setup used for depositing the cylindrical PLD films.
TEM microphotograph of a flat PLD film deposited over simultaneously with one of our cylindrical samples. The small nanograins, , are the constituents of the film. The inset is a digital magnification of a part of the microphotograph.
Total thickness inaccuracy of our measurements of cylindrical PLD films vs the film thickness. There is represented the superposition of: (a) the inaccuracy in the radius of the wire substrate, , (b) the inaccuracy in the spontaneous room temperature magnetization of our PLD films, , and (c) the variable with thickness inaccuracy from the fluxmeter and the oscilloscope of our system. The insets represent the bar of error, for each film thickness, in a logarithmic scale vs the film thickness.
IWE hysteresis loops of our cylindrical PLD films. The dependence of the IWE on the applied torque is shown in Figs. 5(a)–5(c) for a constant amplitude of . The IWE dependence on the circular magnetic field is shown in Figs. 5(d)–5(f), while the applied torque was kept at the saturating value of . Note that from Eq. (3) and the vertical axis can be labelled with the relative magnitudes or .
(a) Linear dependence of the angular deformation of the samples with the applied torque. (b) Dependence of the remanent longitudinal magnetization, normalized to the saturation magnetization, on the applied torque; note the saturation of the IWE. Note also that from Eq. (3) and the vertical axis can be labelled with the relative magnitudes , . The lines are guides to the eye.
(a) A magnetization rotation process which considers a uniaxial magnetic anisotropy in the direction, makes it possible to calculate the longitudinal component of the magnetization, when a circular magnetic field is applied. (b) Fit of our experimental data of the IWE according to the above magnetization rotation process assuming . Note that from Eq. (3) and the vertical axis can be labelled with the relative magnitudes or .
Magnetic domain structures, obtained by the Bitter technique, corresponding to the simultaneously deposited planar films, revealing charged domain walls. The black and white lines correspond to wall with positive and negative divergence of magnetization, respectively. The arrows indicate the spontaneous magnetization direction inside each magnetic domain.
IWE magnetic flux loops corresponding to cylindrical PLD films having different thicknesses. All these loops were saturated with respect to the applied torque and all of them satisfied the conditions for the correspondence shown in Fig. 7. The loop corresponding to the sample with thickness is shown in two different scales. This thickness was the lowest determined from our experiments.
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