Solid State Phenomena Vol. 190

Abstract: In this work we present a new concept for measuring high intensity pulsed magnetic fields (h (t)) through the spectral analysis of spin excitations in a saturated yttrium-iron garnet (YIG) thin film grown on a gadolinium gallium garnet (GGG) substrate. The spectrum of spin excitations, generated in the sample by picosecond h (t), was determined with the help of a magnetooptical (MO) Faraday probe in the guided wave regime of lightwave propagation. This technique, compared to the standard MO cells, allows one to avoid saturation effects because the amplitude of h (t) is measured in the frequency domain, and allows us to realize the analysis in real time taking advantage of strong a MO signal.

Abstract: In this paper the contributions of switching, slide, creep and Debye relaxation modes of the domain wall dynamics to the low-frequency magnetic properties of chiral and racemic [Mn^II(HL-pn)(H₂O)][Mn^III(CN)₆]2H₂O molecular ferrimagnets were distinguished.

Abstract: Recently, it has been shown that the magnetorefractive effect in reflection and transmission modes in La_0.7Ca_0.3MnO₃ manganite thin films and single crystals can reach several percents for single crystals and up to 20-40% for thin films in the middle infrared spectral range near the Curie temperature. In the present paper, to explain these data we used the effective medium approach and supposed that La _0.7Ca _0.3MnO₃ manganites consist of low and high resistivity phases with volume fractions depending on an applied magnetic field. It is shown that the magnetorefractive effect spectra strongly depend on magnetoresistance and optical properties of manganites in the infrared range.

Abstract: We study asymmetrical three-layers F1F2S and F1SF2 structures in an external parallelmag-netic field. Assuming that all F and S layers are dirty, we solve the boundary value problem for theUsadel function. We calculate the critical temperature of in the F1F2S and F1SF2 systems as functionof the F layers thicknesses and external magnetic field.

Abstract: The anisotropic Ising model with competing interactions is investigated in wide temperature range and |J₁/J| parameters by means of Monte-Carlo methods. Static critical exponents of the magnetization, susceptibility, heat capacity, and correlation radius are calculated in the neighborhood of Lifshitz point. According to obtained results a phase diagram is plotted, the coordinates of Lifshitz point are defined, and a character of multicritical behavior of the system is detected.

Abstract: Results of the study of the structural and magnetic properties of periodic Fe/V heterostructures with periods D = 9.4nm and D = 6.3nm are present. The study has shown that ferromagnetic islands are formed on the interfaces of Fe and V. These islands have different magnetic properties as sub-layers of pure iron. Islands in the sample with the period D = 9.4 nm have anisotropic shape, which leads to the anisotropy of magnetic properties.

Abstract: In the frame of Usadel equation the two-dimensional nonlinear boundary problem for heterostructures with complex ferromagnetic (F)/normal metal (N) interlayer has been solved numerically for arbitrary values of electrodes spacing L, thickness d_N and d_F of N and F films. We calculate the current-phase relations for ramp-type S-NF-S and overlap-type SFN-FN-NFS junctions. We have found the range of parameters providing an opportunity for realization of Josephson φ-junction based on the considered structures.

Abstract: We report an investigation of the magnetic phase diagram of the heavy fermion com-pound CeCoGe2.36Si0.64 using DC magnetic susceptibility measurements under high pressure upto 10 kbar. The antiferromagnetic order that develops at ambient pressure below about 5.5 Kremains essentially unaffected by pressure in the investigated pressure range up to 10 kbar. Onthe other hand, moderate magnetic fields appear to induce a quantum critical point in a sam-ple subject to a pressure of 2 kbar. We discuss the role of disorder in the series of compoundsCeCoGe3−xSix.

Abstract: The effect of ferromagnetic layer inhomogeneity on the superconducting resistive transition in Superconductor/Ferromagnet/Superconductor (S/F/S) trilayers is studied. The critical temperature, T_c, and the resistive transition shape versus the F layer thickness, d_F, in Nb/Cu_0.41Ni_0.59/Nb and Nb/Pd_0.81Ni_0.19/Nb trilayers were analyzed. It is shown that the T_c(d_F) dependence is sensitive to the Ni concentration variation along the F layer for thickness of d_F corresponding to the π-superconducting state and to the 0-π crossover thickness.

Abstract: The proximity effect and competition between the BCS and LOFF states are studied in the Cooper limit for thin F/S and F/S/F nanostructures, where F is a ferromagnet and S is a superconductor. The dependences of the critical temperature T_c on the exchange field I, electron correlations λ_f, and the thickness d_f of the F layer are derived for F/S bilayers and F/S/F trilayers. Two new π-phase superconducting states with electronelectron repulsion in the F layers of F/S/F trilayers are predicted. A 2D LOFF state in F/S/F trilayers is possible only in the presence of a weak magnetic field and the appropriate parameters of the F and S layers. The absence of the suppression of 3D superconductivity in short-period Gd/La superlattices is explained and the electronelectron coupling constant in gadolinium is predicted. A method of superconducting probe spectroscopy based on the proximity effect is proposed for determining the symmetry of the order parameter, the magnitude and sign of electron correlations, and the exchange field in various nanomagnets F.