Solid State Phenomena Vol. 215

Abstract: The three-dimensional transition structures in the vortex asymmetric domain walls existing in magnetically uniaxial soft magnetic films with in-plane anisotropy are studied by micromagnetic simulations. It is shown that interaction of closely spaced transition structures results in various dynamical scenarios including vortex-antivortex annihilations, creation and annihilation of singular (Bloch) points, and excitation of nonlinear waves.

Abstract: The technical magnetization and the domain structure of a Tb0.26Y2.74Fe5O12 single crystal have been studied in the temperature region of a spontaneous spin-flip phase transition (SFPT) by magneto-optical method. It has been found that the character of evolution of domain configuration in a SFPT depends from mechanical stresses in crystal.

Abstract: The effect of annealing under applied stress on magnetic properties of Co-based or CoFeNi-based glass-coated microwires was studied. It was found that CoFeNi-based microwires became bistable after annealing because of changing of magnetostriction constant sign, while Co-based microwires keep S-shape of hysteresis loop. The domain wall dynamics of microwires which became bistable was also investigated and it was shown that microwires with acquired bistability are more suitable for applications.

Abstract: The results of study of domain walls oscillations in harmonic magnetic field H = H₀sin (2πft) oriented perpendicular to ferrite garnet (TbErGd)₃(FeAl)₅O₁₂ (111) sample plate for amplitudes that include the drift of domain walls are reported. Numerical modelling of domain walls motion was performed for frequencies f~10² Hz, where the drift is observed experimentally. Comparison of results of numerical modelling with experimental results shows their qualitative agreement. It was established that domain walls oscillations amplitude is a linear function of amplitude of oscillating magnetic field.

Abstract: Magnetic anisotropy of thin films and nanodisk arrays made of cobalt has been studied by the magneto-optical anisometry with modulated field. The improved method of magnetic anisotropy field measurements in thin films has been proposed. This method has been used for cobalt nanodisk arrays in order to investigate anisotropy of magnetization reversal processes due to dipole-dipole interaction between nanodisks.

Abstract: The unique electrical and magnetic properties Fe₈₆Mn₁₃C alloy (Hadfield's steel) are due to special modulated structure. The alloy is widely used in mechanical engineering. Complex studies of the structure and properties of the alloy both in bulk samples and thin-films are suggested to describe the formation of a deformation martensite structure in Fe₈₆Mn₁₃C alloy in the form of self-assembled clusters. It is shown that combinations of anti-ferromagnetic austenite and ferrimagnetic martensite of deformation create unique electric and magnetic properties of Fe₈₆Mn₁₃C alloy both in bulk and in a thin-film state. We seek to explain the reason for the change of the sign of thermoelectric effect depending on temperature. Our task is to investigate thin Fe₈₆Mn₁₃C films as a possible solution to the problems of spintronics.

Abstract: Magnetic nanoparticle heating in alternating magnetic field is the novel approach to the hyperthermia technique for cancer treatment. The accurate measuring of the specific heat absorption rate of the magnetic fluid is the critical issue in the search for efficient materials to minimize the concentration of the magnetic nanoparticles in human tissues. In this work the heat absorption measurement setup consisting of a system of the magnetic field generation, a temperature measuring system, a cooling system, and an external computer control system has been developed. The results of the calibration as well as the results of measurements on the cobalt ferrite nanoparticles are presented.

Abstract: We present a novel method of pattern nanofabrication with high resolution and small shape defects using the traditional electron-beam lithography (EBL) or only a scanning electron microscope (SEM). Our method of Spot EBL is extremely fast, highly scalable on big areas, capable of sub-20 nm resolution and fabrication of polymer patterns with complicated shapes. We show the nanostructure images fabricated by Spot EBL and propose practical applications of the novel method.

Abstract: Metallic particles with outer dimensions smaller than 100 microns in Li-ion battery cannot be detected using a conventional X-ray imaging system. We propose two systems using high Tc SQUIDs: One is a direct detection type and the other is an indirect type. In the direct detection system, an object with a contaminant is magnetized by a permanent magnet and then the remanent field of the contaminant is detected by SQUID. In the indirect detection system, the principle is based on Faradays law of electromagnetic induction. The diameter of the detection coil is 2 to 3 times larger than the SQUID; as a result, less number of SQUIDs, two or three is enough to inspect a specimen with a width of 65 mm. This method is applicable for an inspection of metallic contaminants in non-magnetic film such as a separator for Li-ion battery. We discuss the results of the evaluation of the new system as compared with a direct detection system.

Abstract: In this paper we are reported about a peculiarity of the crystal structure and the magnetic state of TmFeTi₂O₇. The compound TmFeTi₂O₇ has been synthesized using the solid-phase reaction method. Using X-ray diffraction method the disorder in the distribution of the iron ions over five nonequivalent crystal sites was observed, also the populations of the iron atoms positions were determined. We show that below T_f = 6 K the magnetization of TmFeTi₂O₇ depends on the magnetic history of the sample. There are indications for spin glass state. This results allow us to assume the state of spin glass is realized below freezing temperature T_f = 6 K in TmFeTi₂O₇.