Evaluation of Intellectual Property Objects in the Nanoindustry Field

Russian Microelectronics - The recently developed nanomaterials and their production technologies as intellectual property objects (IPOs) are considered. The role of the informational-analytical...     

Anhysteretic magnetization reversal of spin valves with a strong and weak interlayer coupling

The hysteresis of magnetoresistance has been studied as a function of the angle between the magnetic field applied in the plane of layers and the easy axis for spin valves with the composition [Ta, (Ni₈₀Fe₂₀)₆₀Cr₄₀] /Ni₈₀Fe₂₀/Co₉₀Fe₁₀/Cu/Co₉₀Fe₁₀/Mn₇₅Ir₂₅/Ta. In spin valves with a strong interlayer coupling at a small deviation of the magnetic-field direction from the easy axis there was revealed a sharp (to a few tenths of an oersted) narrowing of the hysteresis loop of the magnetization reversal of the free layer. Based on an analysis of the angular dependences of the hysteresis, critical angles at which a change occurs in the mode of the magnetization reversal have been determined. In terms of the Stoner-Wohlfarth model of the coherent rotation of the magnetization, the angles at which a transition to an anhysteretic magnetization reversal is observed have been estimated theoretically for the spin valves with a strong interlayer coupling.     

Effect of yttrium doping on the resistivity and magnetoresistance of La<Subscript>0.80</Subscript>Sr<Subscript>0.20</Subscript>MnO<Subscript>3</Subscript>

The temperature and magnetic field dependence of resistivity of crystals of nominal compositions of La_0.75Y_0.05Sr_0.20MnO₃ grown by floating zone method at different growth rates are studied. The yttrium doping is found to result in the decrease of Curie temperature, suppression of the Pnma-R $ \bar 3 $ \bar 3 c structural transition, increase of resistivity and magnetoresistance. It is shown that the physical properties of the manganites studied are determined by not only the nominal composition but also the growth rate.     

Giant magnetic impedance of wires with a thin magnetic coating

In this review, we analyzed and generalized the results of experimental investigations of physical processes that occur in composite wires with a thin magnetic coating under the conditions of the appearance in them of a giant magnetoimpedance (GMI) effect. Principles of the measurements of high-frequency impedance are described in short; basic definitions are given, and the differences in the linear and nonlinear GMI regimes are described. Data are systemized on the giant magnetic impedance of wires with a thin magnetic coating (composite materials) under the conditions of a strong nonlinearity of the GMI effect, which is accompanied by the appearance of higher harmonics in the output signal. The extremely high susceptibility of the harmonic parameters to external actions can be used in the technical applications for creating ultrasensitive detectors of low magnetic fields. Special attention is paid to model calculations, which confirm the fact that the experimentally observed features of a nonlinear GMI effect are connected with the high sensitivity of the magnetic system to a circular magnetic field near the spin-reorientation phase transitions. Fine features of the effective magnetic anisotropy can play the key role and therefore cannot be ignored in the general case.     

Ferromagnetic manganites La<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Ca<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>MnO<Subscript>3</Subscript>

A brief review of properties of the ferromagnetic manganites La_{1 − x} Ca _x MnO₃ is given. Lattice properties, magnetic properties, transport phenomena, magnetic resonance, and the results of neutron diffraction and optical studies are considered. Special attention is paid to effects observed near the Curie temperature.     

Automatic system for regulating the frequency and power of the 500 MW coal-dust power generating units at the Reftinskaya GRÉS

The monitoring and control systems at the 500 MW coal-dust power generating units No. 7, 8, and 9 at the Reftinskaya GRéS have been modernized using information-regulator systems. Layouts for instrumental construction of these systems and expanded algorithmic schemes for the automatic frequency and power control system and for the boiler supply and fuelling are discussed. Results from tests and normal operation of the automatic frequency and power control system are presented. Translated from élektricheskie Stantsii, February 2009, No. 2, pp. 47–53.     

Magnetooptical Properties of Ferro- and Ferrimagnetic Spinels

Physics of Metals and Metallography - The study of the magnetooptical properties of magnetics in polarized and natural light is important because of a number of urgent problems in the fields of...     

Elastic and magnetic properties of single-crystal La0.4Pr0.3Ca0.3MnO0.3

Results are reported on the experimental investigation of the temperature dependences of the magnetization, velocity of longitudinal sound, and internal friction of single-crystal La_0.4Pr_0.3Ca_0.3MnO_0.3. In the paramagnetic region, extended temperature hysteresis of the sound velocity has been revealed, which is due to a nonequilibrium state of the crystal structure of the compound.     

Transport phenomena in the La<Subscript>0.72</Subscript>Ba<Subscript>0.28</Subscript>MnO<Subscript>3</Subscript> single crystal

Results of an experimental study of the temperature dependences of the magnetization M, electrical resistivity, magnetoresistance, thermo-and magnetothermo-emf, and Hall effect of the La_0.72Ba_0.28MnO₃ single crystal are presented. An analysis of the temperature dependences of kinetic properties shows that, at low temperatures, electrons are principal charge carriers in La_0.72Ba_0.28MnO₃ and the metallic conduction takes place. As the temperature increases to T ≈ 145 K, the sign of the ordinary Hall coefficient reverses; this indicates the change in the type of the majority charge carriers. Within a certain temperature range which lies substantially below the Curie temperature (T _C ), a metal-semiconductor transition occurs. Near the Curie temperature and within the paramagnetic range, the manganite under study is a semiconductor; the conduction is mainly effected by holes activated to the mobility edge. The critical behavior of the resistance and magnetoresistance is discussed.     

Influence of a Domain Wall on the Spin Polarization of Electric Current

Physics of Metals and Metallography - The spin polarization of charge carriers moving in a ferromagnet through a 180° Bloch domain wall is calculated. It is demonstrated that a magnetization...