Scanning thermal microscope-detected ferromagnetic resonance (SThM-FMR) combines a thermal near-field microscope with a FMR spectrometer and detects the thermal response due to resonant microwave absorption by measuring the resistivity change in the thermal nanoprobe. The advantage of this technique is to provide imaging capabilities at fixed resonance conditions as well as local microwave spectroscopy at the nanoscale. A technique that uses the same setup but detects the thermoelastic response of the sample is the scanning thermoelastic microscope-detected FMR (SThEM-FMR). This latter technique is advantageous when FMR spectra of single nanostructures have to be recorded at a fixed position. The experimental setups and the signal generation processes of SThM/SThEM-FMR are described in detail. With the SThM-FMR setups a temperature resolution of and a local resolution of are actually achieved. With SThEM-FMR the obtained local resolution is . The detection limits of both techniques can be as low as spins. To demonstrate the potential of these new techniques SThM/SThEM-FMR investigations of local magnetic anisotropies, magnetization dynamics of single nanodots and inhomogeneous FMR excitations due to finite size effects are presented. Simultaneously, information on the magnetic parameters, the topography, and the thermal properties is provided. To describe the further potential of this recently developed SThM-FMR technique, combined magnetoresistance and FMR investigations are presented and an outlook on possible future applications is given.
The author would like to thank the members of the group of Professor J. Pelzl at the Ruhr-University-Bochum Germany and the group of Professor J.P. Bucher of the University of Strasbourg France for the assistance with the measurements. Dr. O. von Geisau, Dr. D. Spoddig, and B.K. Bein are acknowledged for carefully reading this manuscript. This work was supported by the SFB 491: Magnetic Heterostructures: Spinstructure and Spintransport.
A. Motivation for dynamic magnetic characterization at nanoscale
II. SCANNING NEAR-FIELD THERMAL MICROSCOPY AND INVESTIGATED THERMAL PARAMETERS
A. Theory for thermal wave microscopy
B. Experimental techniques of thermal wave microscopy
III. BASICS OF FERROMAGNETIC RESONANCE
IV. DETECTION OF MICROWAVE ABSORPTION BY SCANNING THERMAL MICROSCOPY (METHODOLOGY)
A. Basic setup joining SThM and FMR
B. Setup based on conventional AFM for high imaging quality
C. Setup based on self-built AFM/STM for local FMR spectroscopy
D. SThEM-FMR realized by STM detection
V. INVESTIGATION OF FERROMAGNETIC RESONANCE EXCITATIONS IN SINGLE NANOSTRUCTURES
A. Local detection of FMR spectra in single Fe nanostructures by the active thermal modulation technique TM-FMR
1. Local magnetic anisotropy changes in an epitaxial Fe mesa structure correlated with the nanotailored substrate structure deduced by PM-FMR
2. Lateral correlation of oxidation stages of an epitaxial Fe film deduced by AFM supported TM-FMR
B. Magnetization dynamics of single Ni nanodots measured by SThEM-FMR
C. Simultaneous local detection of magnetic anisotropies and magnetoresistance in Ni nanowires
D. Local influences of orientation and stray fields of Py lattices on the FMR of a single Py stripe
E. Nano scaled inhomogeneous FMR excitation in a Co stripe based on finite size effects
VI. OTHER TECHNIQUES FOR LOCALLY RESOLVED DYNAMIC MAGNETIC MEASUREMENTS
A. Photothermally modulated (PM) FMR
B. Brillouin light scattering (BLS)
C. Time-resolved magneto-optical Kerr effect (TR-MOKE)
D. X-ray magnetic circular dichroism (XMCD)
E. Magnetic force resonance microscopy (MFRM)
F. Near-field microwave spectroscopy
G. Spin-polarized scanning tunnel microscopy (SP-STM)
VII. CONCLUSION AND OUTLOOK
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