This study explores magnetization exhibited by nanoscale platinum-based structures embedded in pure silica plates. A superposition of laser pulses in the samples produced periodic linear arrangements of micro-sized structures. The samples were integrated by PtO2 microstructures (PtOΣs) with dispersed Pt oxide nanoparticles in their surroundings. The characterization of the materials was performed by high transmission electron microscopy studies. Furthermore, topographical and magnetic effects on the sample surfaces were analyzed by atomic force microscopy and magnetic force microscopy, respectively. The magnetic measurements indicated an enhancement in the gradient phase shift and in the gradient force related to the magnetic PtOΣs. The possibility of tuning the magnetic characteristics of the samples through contact with a Nd2Fe14B magnet was demonstrated. This process corresponds to an innovative method for obtaining magnetic PtOΣs induced by laser pulses. Moreover, an increase in the compactness of the silica with platinum-based structures was confirmed by an evaluation of the effective elastic modulus with reference to pure silica. The multimodal magnetic structures studied in this work seem to be candidates for developing high-density magnetic storage media.

Amplitude modulation (AM) scanning force microscopy (SFM) is superior to frequency modulation SFM in simplicity, sensitivity, and stability, but is still replaced by the latter because it is too slow when the Q factor is high (bandwidth < 0.5 Hz for Q > 50,000 and resonant frequency ω0 < 50 kHz). We report a close-loop AM detector that has an 18 Hz bandwidth, better than 1 mHz frequency resolution and excellent response to step frequency changes even for Q ∼ 60,000 and ω0 ∼ 32 kHz. Its superiority is well shown by the comparison of magnetic force microscope images taken under the new and old AM detection modes with the tip and scan area (videotape sample) being unchanged. Also important is that shifting the driving frequency from near the resonance peak to further away from the peak does not decrease the frequency resolution as much as we expect (but can increase the response speed).

Magnetic force microscopy (MFM) is a well-established technique for imaging the magnetic structures of small magnetic particles. In cooperation with external magnetic fields, MFM can be used to study the magnetization switching mechanism of submicrometer-sized magnetic particles. Various MFM techniques allow the measurement of a hysteresis curve of an individual particle, which can then be compared to ensemble measurements. The advantage of using MFM-constructed hysteresis loops is that one can in principle understand the origin of dispersion in switching fields. It is also possible to directly observe the correlation between magnetic particles through careful imaging and control of the external magnetic field. In all of these measurements, attention needs to be paid to avoid artifacts that result from the unavoidable magnetic tip stray field. Control can be achieved by optimizing the MFM operation mode as well as the tip parameters. It is even possible to use the tip stray field to locally and reproducibly manipulate the magnetic-moment state of small particles. In this article, we illustrate these concepts and issues by studying various lithographically patterned magnetic nanoparticles, thus demonstrating the versatility of MFM for imaging, manipulation, and spectroscopic measurements of small particles.