The use of a piezoelectric force sensor in the magnetic force microscopy of thin permalloy films.

A piezoelectric force sensor is suggested for magnetic force microscopy (MFM) purposes. Added between the piezoelectric resonator and the magnetic probe is a mechanical force amplifier in the form of a thin, long resonant arm with an integral micro-rod whereby the amplitude of the force acting on the probe is amplified by a factor of 20 to 40 at a low noise level. When the sensor was operated in air, its noise floor was found to be 1.4 pN (RMS) at a bandwidth of 100 Hz. The piezoelectric sensor requires no repeated calibration; and it is capable of operating in a vacuum, and at cryogenic temperatures. By using this sensor we carried out the MFM of ultrathin (1.5- and 3-nm-thick) Ni79Fe21 permalloy films. The 1.5-nm-thick permalloy films studied have a nanoisland structure, whereas 3-nm-thick ones are contiouous. Domain structures were found in both. The MFM image was found to suffer substantial changes when the external magnetic field was altered by 1 Oe. The structures under study featured both "elastic" and "viscous" magnetic force components.

Relaxation Properties of Contrast Media for MRI Based on Iron Oxide Nanoparticles in Different Magnetic Fields.

We studied dependences of T2 relaxation time on magnetic field and concentration of nanoparticles. It was found that nanocontrast media are effective under the influence of the magnetic fields in the range 0.3-7 T. Data of electron paramagnetic resonance confirm the assumption on aggregation of nanoparticles not coated with proteins in high magnetic fields.

Contrast Agents Based on Iron Oxide Nanoparticles for Clinical Magnetic Resonance Imaging.

Magnetic resonance imaging (MRI) is one of the most perspective methods of noninvasive visualization in medicine, and use of contrast agents significantly its potentialities extends. Iron oxide nanoparticles are promising contrast agents, but in fact all the data on their efficiency were obtained in high-field tomographs for experimental animals. We studied the possibility of using magnetic nanoparticles for MRI visualization of rat brain glioblastoma at the most common clinical field 1.5 T The data indicate the efficiency of iron oxide magnetic nanoparticles as contrast agents for 1.5 T MR tomographs.

Inertial motor on a single piezoelectric actuator for a low-temperature near-field scanning optical microscope.

The impact of such factors as the shape of the applied voltage pulse, the friction force, and the mass of the movable part on the motor operation at low temperatures is experimentally investigated. Important added features in the motor design are support springs. These springs prevent one part of the slider clamp from shifting relative to the other during motion. The optimization of the factors listed above provided for reliable withdrawal of the microscope's fiber probe with a speed of up to 0.2 µm/step at a temperature of 5 K.

Anomalous multi-order Raman scattering in LaMnO3: a signature of quantum lattice effects in a Jahn-Teller crystal.

The multi-order Raman scattering is studied up to fourth order for a detwinned LaMnO3 crystal. Based on a comprehensive data analysis of the polarization-dependent Raman spectra, we show that the anomalous features in the multi-order scattering could be the sidebands on the low-energy mode at about 25 cm(-1). We suggest that this low-energy mode stems from the tunneling transition between the potential energy minima arising near the Jahn-Teller Mn(3+) ion due to the lattice anharmonicity and that the multi-order scattering is activated by this low-energy electronic motion. The sidebands are dominated by the oxygen contribution to the phonon density-of-states, however, there is an admixture of an additional component, which may arise from coupling between the low-energy electronic motion and the vibrational modes.

Collective behavior of light-induced droplets in smectic membranes.

Collective behavior and organization of droplets in thin smectic membranes were investigated using polarized light microscopy. Droplets were nucleated in membranes by light illumination. We observed the formation of periodic hexagonal and square lattice structures from droplets at large droplet concentration. Nearly linear dependence between period of structure and droplet size was found. We observed that droplets are nucleated on dislocations and periodic chain of droplets may be formed along a dislocation.