Lateral and depth-dependent thermal diffusion length vs size of thermal source at a constant heating modulation frequency of .
Schematic of a semi-infinite silicon substrate with a magnetic nanostructure consisting of a Py-stripe of limited dimensions (, , ), representing the modulated homogeneous heat source. The component of the Py film is not shown in the figure due to its small size.
Lateral thermal wave distribution perpendicular to the stripe (as shown in the inserted sketch) calculated for a modulated heat source of finite dimensions, in ideal thermal contact with semi-infinite silicon substrate. The heating modulation frequencies are varied from (red line) to (blue line).
Techniques of thermal microscopy (from left to right): schematic of thermoreflectance (TR), scanning thermal microscopy (SThM), and scanning thermoelastic microscopy (SThEM).
SEM images of two commercially available SThM probes: (a) Wollaston wires with Pt tip from Veeco; (b) coated Si tip from PSIA.
Scheme of ferromagnetic resonance measurement. The magnetization precession in the sample is illustrated with driving microwave field distribution in the surrounding cavity.
Illustration of the principle of demagnetizing field. An externally applied field leads to a virtual polarization of the edges of the sample S,N. The white area represents a small area of the ferromagnetic material which sees a demagnetizing field resulting from this polarization.
Precession of relaxing magnetization vector illustrating the Landau Lifshitz Gilbert [Eq. (4)].
Scheme of the SThM-FMR setup.
Cavity with waveguide part of setup.
Design of the cavity top.
Schema of the Explorer setup providing optimal scanning abilities.
Pictures of the Explorer setup. left: top view of the FMR part with open cavity and removed AFM; right: side view of the explorer setup with AFM placed on the FMR part; bottom: thermal probe placed on a magnetic nanostructure in the cavity taken by the camera of the Explorer.
Picture of the SThM-FMR setup capable of local FMR spectroscopy. The inset shows the mounted thermal nano probe and the larger cavity hole.
Scheme of the SThEM-FMR.
Picture of the STM scan head mounted on the Nanocube.
Sketch of the PM-FMR setup.
Typical PM-FMR signal.
Top: Optical microscope image of structured Fe surface. Bottom: Gray scale image of the field independent PM-FMR-amplitude. The spots marked by a and b indicate the position for the PM-FMR spectra provided in Fig. 20.
Amplitude of FMR response versus applied magnetic field. Spectra top to bottom: Integral conventional FMR, PM-FMR of Fe mesa on pure GaAs marked by a in Fig. 19, PM-FMR spectrum of Fe-mesa with HEMT below marked by b in Fig. 19.
Left: Sketch of the Fe film sample prepared by molecular beam epitaxy, including the two different oxidation stages due to the removal of the two top layers. Right: Optical microscope image of the sample under investigations. The dark blue areas are regions where the protecting ZnS film is still in place. In the white shining areas only Ag is covering the Fe film. In the brown rough areas iron has been completely oxidized.
FMR spectra of the Fe film. Upper three spectra: Derivative of the resonance absorption of the TM-FMR: (from top to bottom) uncovered Fe, Ag-covered area, and ZnS-protected area of the sample. Lower spectrum: conventional amplitude modulated FMR. The dashed lines indicate the pure Fe line position and the dash-dotted line the shifted resonance of the spectrum for the Ag-covered area.
Illustrating model of the sample structure: Au is evaporated on mica and flame annealed. On top Ni is grown electrolytically forming differently shaped dots in a Ni film matrix. Each dot is a separate heat source for the thermoelastic expansion while in FMR.
Topography of the Ni film grown on a (111)-textured flash annealed Au film grown on a mica substrate. The blue and the red markers give the position for the SThEM-FMR measurements shown in Fig. 25
Red and blue lines represent SThEM-FMR spectra taken at the red and blue marked spots in Fig. 24. The black line is the conventional FMR spectrum of the whole sample measured by the microwave diode given in arbitrary units.
Frequency dependence of the FMR line width: black dots represent the linewidth measured by conventional FMR at three different frequencies. The upper black line represents the fit to the line width due to the equation. The lower black line represents the slope of the fit with subtracted representing the frequency dependence of the intrinsic part of damping. The dotted red line give the intrinsic part of the line width at a microwave frequency of .
Sketch of the combined MR and SThM-FMR setup.
FMR investigations of Ni wires: (a) conventional angle dependent FMR on a Ni wire. (c) Locally resolved SThM-FMR spectra of the thick end of the Ni-wire . (d) of the thin part of the constricted Ni-wire . The spectra correspond to positions 1 and 4 in the scheme marked by (b). The microscope pictures show the thermal nanoprobe on the wire during SThM-FMR measurement.
Relative magnetoresistance curves for positive increasing field only. The different curves are measured at the AFM probe positions on the Ni wire marked by numbers related to the scheme above.
Scanning electron microscope image of the Py-stripe lattice.
Amplitude modulated conventional FMR measured in the SThM-FMR setup providing the resonance fields marked by the dashed lines for the SThM-FMR images of Fig. 32.
AFM topography (left) and thermal images of SThM-FMR (right) for different applied resonance fields of Fig. 31.
Sketch of the Co stripes on Si. The dimension of a Co stripe is , the distance between the stripes is .
Image of the angle dependent conventional FMR investigation of the Co-stripe lattice. The FMR absorption amplitude is plotted in rainbow colors against the in-plane angle on the axis and the external field on the axis. The arrows mark the four resonance line positions for the external field applied perpendicular to the stripes (compare Fig. 33).
Conventional FMR absorption spectrum taken in the SThM-FMR setup for external field perpendicular to the Co stripes. The four observed resonances are marked according to Fig. 34.
Calculated FMR frequency spectrum for applied external field perpendicular to the Co stripes deduced by Fourier transformation from the oscillating magnetization component in the direction of the microwave magnetic field displayed in the inset. I–III mark the resonances according to Figs. 34 and 35.
SThM-FMR image of the uniform excitation marked by III in the Figs. 34–36. The size of the image is .
SThM-FMR image of the rim-excitation marked by I in the Figs. 34–36. The size of the image is .
Illustrations of the estimation for the temperature distribution perpendicular to the Co stripe due to the rim excitation. Upper part calculated magnetization distribution for the applied resonance field of . Lower part calculated temperature distribution taking into account the magnetization distribution above (Ref. 63).
SThM-FMR image of a Co stripe taken at the resonance field of the backward volume mode marked by II in the Figs. 34–36. The size of the image is . Thermal amplitude and phase images are taken simultaneously not at an edge of the stripe to better prove the exponential decay of the amplitude towards the middle of the stripe and the homogeneity of the phase across the stripe.
SThM-FMR image of the edge of a Co stripe taken at the resonance field of the not-aligned mode as marked in the conventional FMR spectra of Figs. 34 and 35. The size of the image is . The simultaneously recorded AFM image is displayed on the right, the thermal amplitude is displayed on the left.
Characteristics of locally resolved measurement techniques for the investigation of magnetic dynamics.
Article metrics loading...
Full text loading...