Solid State Phenomena Vol. 215

Abstract: Spin injection mechanisms for radiation and detection of terahertz waves based on magnetic nano junction are considered. High efficiency of terahertz radiation is theoretically explained and the method of the detection of this radiation is offered. The device of the spin injected terahertz radiators is presented.

Abstract: The present study investigates photoinduced changes of magnetostriction in yttrium-iron garnet (YIG) single crystals. Single crystals of Y₃Fe₅O₁₂ were grown from BaO-B₂O₃ (YIG(Ba)), PbO-PbF₂ (YIG(Pb)) and PbO-PbF₂:SiO₂ (YIG(Si)) solutions from flux. Photoinduced magnetostrictive response types for these three kinds of YIG crystals are quite different. The magnetostrictive constants, the trigonal symmetric internal stresses and their photoinduced changes were calculated for all samples. The conclusion is that the internal stresses in the crystal lattice, caused by defects, determine the photoinduced response type of the crystal.

Abstract: Thermopower α and magnetothermopower α/α were studied in the single-crystal Sm_0.55Sr_0.45MnO₃ samples, containing clusters of three types: ferromagnetic clusters with the Curie temperature T_C = 134 K, A-type antiferromagnetic clusters with the Neel temperature T_NA T_C and CE-type antiferromagnetic clusters with the T_NCE = 240 K. The curves of temperature dependence of α (T) and {α/α}(T) have extrema in the T_NCE-region: large maximum on the first and sharp minimum on the second. Negative magnetothermopower in minimum achieves the giant value 50% in magnetic field 13,2 kOe. It is shown that thermopower is essentially caused by the presence of CE-type antiferromagnetic clusters, in which exists charge order, displacing oxygen ions

Abstract: Magnetic properties and magnetoimpedance were studied for as-cast Fe₅Co₇₅Si₄B₁₆ rapidly quenched amorphous ribbons and Fe₅Co₇₅Si₄B₁₆/polymer amorphous ribbon based composites with the following polymer coverings: modified rubber solution in o-xylene, copolymer solution of butyl methacrylate and methacrylic acid in isopropanol and solution of polymethylphenyl resin in toluene. All selected composites showed very good adhesion of the coverings and allowed us to provide long term temperature measurements, including measurements under stress. Polymer coverings have an effect on the temperature sensitivity of the impedance value. The present study demonstrates the promising future for the development of magnetically active conductor/polymer composites for creating new sensors. Modification of the composition and thickness of the polymer coverings can be the basis for creation of the detectors with a unique set of functional properties. Polymer covering can perform the protective and reinforcing role that is particularly important in the case of nanocrystalline alloys and the polymer covering can also affect and improve the functional properties of the magnetic core.

Abstract: The magnetorefractive effect (MRE) has been measured in the infrared spectral region of 1.2-28 μm in MBE-grown Fe/Cr superlattices with variable Fe and Cr layers thicknesses in p-polarized light. The magnetic and magnetooptical properties have been studied as well. From the MRE spectra modeling in the framework of magnetoreflection theory for multilayered structures, the parameters of interfacial spin dependent scattering of conductivity electrons have been defined for different types of exchange coupling between adjacent Fe layers. The dependence of interfacial scattering parameters on Fe and Cr layer thickness is discussed.

Abstract: The influence of the temperature, elastic tensile stresses and external magnetic field on the impedance of amorphous Co₇₅Fe₅Si₄B₁₆ ribbons was studied. It was observed that the character of the elastic tensile stresses influences the impedance and its changes in the external magnetic field are determined by a temperature of the ribbons. It was shown that changes of the stressimpedance character and magnetoimpedance temperature dependences were caused by a change in the sign of a magnetostriction constant with the temperature.

Abstract: Magnetic properties and magnetoimpedance of [FeNi/Cu]_n/FeNi/Cu (500 nm)/[FeNi/Cu]_m/FeNi MI asymmetric and symmetric structures were studied for multilayeres with different thickness (25, 50 or 170 nm) of permalloy layers. The asymmetric structures in the case of FeNi layers of 50 nm show higher sensitivities comparing with symmetric structures. Asymmetric multilayered structures with 25 nm thick FeNi layers are an interesting subject for further investigation as the interactions between FeNi layers seem to be providing the best MI response.

Abstract: The magnetic and electrical properties of Co/Ge bilayer films are experimentally studied. It is established that at the Co/Ge interface an intermediate magnetic layer forms. This layer affects the magnetic behavior and magnetoresistive effect in the investigated structures.

Abstract: The main features of the magnetic, magnetoelastic and record magnetoelectric properties of a HoAl₃(BO₃)₄ alumoborate single crystal have been studied experimentally and theoretically. For B||a we have observed a giant polarization ΔP_ba(B_a) ≈ –5240 µС/m² induced by field of 9 T at T = 5 K. We have calculated the magnetic characteristics of HoAl₃(BO₃)₄ in the framework of a crystal-field model. The parameters of the crystal-field in HoAl₃(BO₃)₄ have been determined. Good agreement of experimental and calculational magnetization curves M_c,^с(В) and the temperature dependences of magnetization M_с,^с(T) was achieved. For interpretation of magnetostriction in HoAl₃(BO₃)₄ the field and temperature dependences of the multipole moments have been calculated.

Abstract: Structural features of interfaces in [Co/Cu]_n superlattices obtained by magnetron sputtering have been studied by nuclear magnetic resonance (NMR). Modification of interface structural characteristics and magnetoresistive properties of the superlattices with the increase of the number of [Co/C] bilayers is analyzed. Correlation between magnetoresistance and interface structural characteristics has been revealed.