Solid State Phenomena Vols. 152-153

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https://doi.org/10.4028/www.scientific.net/SSP.152-153

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Effect of Heat-Treatment on the Phases of Ni-Mn-Ga Magnetic Shape Memory Alloys

Authors: Pnina Ari-Gur, Giora Kimmel, James W. Richardson, Ashfia Huq, Kapil Sharma

Abstract: The Heusler alloys Ni50Mn25+xGa25-x display magnetic shape memory effect (MSM) with very fast and large reversible strain under magnetic fields. This large strain and the speed of reaction make MSM alloys attractive as smart materials. Our crystallographic investigation of these alloys, focused on non-stoichiometric composition with excess of manganese. Using neutron diffraction, we revealed the necessary processing parameters to achieve and preserve the homogeneous metastable one-phase martensitic structure that is needed for an MSM effect at room temperature.

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Magneto-Optical Effects in Excitonic One-Dimensional Structures

Authors: S.G. Erokhin, L.D. Deych, A.A. Lisyansky, A.B. Granovsky

Abstract: We present results of a theoretical investigation of magneto-optical properties in one-dimensional magnetophotonic crystals containing a quantum well defect. In contrast to garnet based magnetophotonic crystals, our proposed structures can be tuned not only by the magnetic field but also by the electric field, illumination, and irradiation. The developed algorithm can be applied to arbitrary magneto-optical effects in multiple quantum well periodic structures. Using this algorithm we demonstrate that the Fabry-Perot exciton resonator structure significantly enhances the Faraday effect and can be used as a highly efficient modulator of light.

503

Second Harmonic Generation in Core (Shell) γ-Fe₂O₃(Au) Nanoparticles

Authors: I.A. Kolmychek, T.V. Murzina, S. Fourier, J. Wouters, V.K. Valev, T. Verbiest, O.A. Aktsipetrov

Abstract: The films containing core (shell) γ-Fe2O3 (Au) nanoparticles that possess the plasmon resonance at the wavelength 550 nm are prepared. The second harmonic generation in these structures is shown to be diffuse and depolarized, that is typical for the hyper-Rayleigh scattering.. The studies of the magnetization-induced second harmonic generation shows that the ratio of the magnetic to nonmagnetic components of the hyperpolarizability of a single nanoparticle, γM/γ0 ~ 0.4 in the field of about 3 kOe.

508

π Phase Superconductivity and Magnetism in Ferromagnet / Superconductor / Ferromagnet Trilayers

Authors: Mansur G. Khusainov, Yurii N. Proshin

Abstract: On the base of new boundary-value problem for the Eilenberger function we investigate the superconducting and magnetic states in ferromagnet/superconductor (FM/S) nanostructures, where superconductivity is a superposition of the BCS pairing with zero total momentum in the S layers and the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) pairing with nonzero 3D coherent momentum k in the FM layers. We originally study the interplay between the BCS and FFLO states in the pure thin FM/S/FM trilayers and two novel -phase superconducting states with electron-electron repulsion in the FM layers are predicted. The modulated FFLO states are possible in such trilayers only in presence of external magnetic field at suitable parameters of the FM and S layers. In the FM/S superlattices there are also two -phase magnetic states (0 and ) with compensation of the exchange field paramagnetic effect. This fact allows us to explain a surprisingly high Tc ~ 5K in the short period Gd/La superlattice and to predict the sign and value of the electron-electron interaction in the ferromagnetic Gd metal.

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The Reflectance Spectra of Photonic Crystals with Embedded Ferrite Inclusions

Authors: Vladimir Gorelik, N.I. Yurasov, Y.P. Voinov, M.I. Samoilovich, V.V. Gryasnov

Abstract: Results of optical properties investigations of photonic crystals, filled by ferrites, are presented. The photonic crystals consist of amorphous SiO2 spherical nanoclusters. Pores of the crystals were filled by ferrites , where . Reflectance spectra were studied in visible range. It was shown that the reflectivity of the fabricated magnetophotonic crystals increases up to 80% under magnetization.

518

Hall Effect in LaB₆ and NdB₆

Authors: M.A. Anisimov, A.V. Bogach, V.V. Glushkov, S.V. Demishev, N.A. Samarin, N.Y. Shitsevalova, N.E. Sluchanko

Abstract: To shed more light on the peculiarities of ground state formation in RB6 Hall effect in NdB6 and LaB6 has been investigated on the single crystals at temperatures 2K for LaB6 and <100> for NdB6). A very similar temperature behavior of RH(T) with the step–like anomaly near T ~ 25K has been established for both magnetic NdB6 and diamagnetic LaB6 at intermediate temperatures T>10K. The temperature independent behaviour of Hall coefficient (RH(LaB6) ~ –3.6•10-4 cm3/C, RH(NdB6) ~ –3.7•10-4 cm3/C) observed in the interval 10K

525

Magnetic Force Microscopic Study on Domain-Wall Molecules in NiFe Nano Rings

Authors: Kohei Sasage, Naoya Okamoto, Hana Tsujikawa, Takehiro Yamaoka, Eiji Saitoh

Abstract: A pair of magnetic domain walls (DWs) in ferromagnetic NiFe rings has been investigated in terms of the magnetic force microscopy (MFM). When the distance between the rings d is greater than a threshold value dth, MFM signals indicate that a DW in the ring is dragged due to a stray magnetic field from an MFM probe tip. When d < dth, this drag signals disappears; DWs are bound to each other by the DW-DW interaction. This transition can be argued in terms of the competition between the DW-DW magnetostatic interaction and the DW-drag potential. From the d-dependent MFM data, the DW-drag potential was estimated.

529

Ab Initio Study of Electronic and Magnetic Properties of GaSb/Mn and GaAs/Mn Digital Ferromagnetic Heterostructures

Authors: A. Titov, E.T. Kulatov, Y.A. Uspenskii, V.V. Tugushev, F. Michelini, H. Mariette

Abstract: Electronic and magnetic properties of GaSb/Mn and GaAs/Mn digital heterostructures were studied using the augmented plane wave method. The calculated electronic structures of GaSb/Mn and GaAs/Mn are similar. A pre-edge absorption line at 6541 eV should be observed in Mn K-edge x-ray absorption spectra of the heterostructures. This line can be used to study the spatial distribution of Mn in layers. The energy of exchange interaction between two Mn layers was calculated as a function of interlayer separation. Different dependencies of the exchange energy are found for GaSb/Mn and GaAs/Mn heterostructures.

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X-Ray Diagnostics of Magnetic Semiconductor Quantum Well Structures

Authors: I.A. Likhachev, E.M. Pashaev, M. A. Chuev, I.A. Subbotin, V.V. Kvardkov, B.A. Aronzon, V.V. Rylkov, A.Ye. Golovanov, M.A. Pankov

Abstract: In the present contribution the results of the high-resolution X-ray diffraction and X-ray glancing-incidence mirror reflection studies of structural characteristics of the quantum-well GaAs/Ga1-xInxAs/GaAs diluted magnetic semiconductors (DMSC) are presented. The influence of the real structure of the samples on their electro-physical properties is discussed.

537

High Field Magnetoresistance Behavior in PrB₆ and NdB₆

Authors: M.A. Anisimov, V.V. Glushkov, S.V. Demishev, N.A. Samarin, N.Y. Shitsevalova, N.E. Sluchanko

Abstract: The comprehensive study of low temperature magnetoresistance (MR) has been carried out on high quality PrB6 and NdB6 single crystals at temperatures 2–20K and in magnetic fields up to 8T. The negative MR (Δρ/ρ<0) was found in the paramagnetic state at T>TN for both compounds. The analysis of the experimental data allows us to establish three contributions to MR. In addition to the main Brillouin type negative component –Δρ/ρ~Mloc2~H2 which may be interpreted in terms of Yosida theory [Phys. Rev. 107 (1957) 396] both the linear and nonlinear magnetic contributions were also deduced. According to detailed analysis in the framework of spin–polaron approach proposed by A.V. Bogach et al. [Physica B 378–380 (1957) 769] the last component should be ascribed to the ferromagnetic (FM) nanodomains embedded in the metallic RB6 matrix. The estimation of local magnetic susceptibility χloc=(–1/H•(d(Δρ/ρ)/dH))1/2 is deduced directly from the quadratic part of negative MR and reveals Curie–Weiss type behaviour in paramagnetic (PM) phase with paramagnetic Curie temperatures Θp~– 22K and –31K for PrB6 and NdB6 correspondingly. The results of undertaken analysis allow to conclude in favour of the concurrence between AF and FM iteractions as the main reason of incommensurate (IC) magnetic structure formation in RB6.

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