Papers by Keyword: Colossal Magnetoresistance

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Authors: M. Auslender
Abstract: It is shown that in colossal magnetoresistance materials an inhomogeneous alternating magnetic field generates a strong electric field of non-inductive nature. This magnetoelectric effect is an analog of acoustoelectric effect in conventional semiconductors. Due to the above electric field spin waves in the former materials, like acoustic waves in the latter ones, acquire an additional attenuation at equilibrium. This attenuation may be converted to amplification by applying strong enough dc electric field drifting the carriers (solid-state Cherenkov’s effect). The experiments, which probed this phenomenon in HgCr2Se4 using spin wave pumping, are discussed.
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Authors: S.-G. Eriksson, S. Ivanov, J. Eriksen, M. Valkeapää, Lars Gunnar Johansson, Håkan Rundlöf, R. McGreevy, P. Berastegui, P. Björnsson, M. Rubhausen, J. Bäckström, M. Käll, L. Börjesson
505
Authors: V.V. Glushkov, M.A. Anisimov, A.V. Bogach, S.V. Demishev, N.A. Samarin, A.V. Kuznetsov, A.V. Dukhnenko, A.V. Levchenko, N.Y. Shitsevalova, K. Flachbart, N.E. Sluchanko
Abstract: The transport and magnetic properties of the Eu1-xCaxB6 (0x0.4) single crystals were studied in the wide ranges of temperatures (1.8-300 K) and magnetic fields (up to 8 T). The experimental data allow to identify a metal-insulator transition (MIT) at the critical Ca concentration xMIT≈0.3, which agrees well with the predictions of double exchange model (V.M. Pereira et al. Phys. Rev. Lett., 93 (2004) 147202). A significant enhancement of magnetoresistive effect is observed below 100K for Eu1-xCaxB6 compounds corresponding to the metallic side of the MIT (xxMIT). The drastic decrease of paramagnetic Curie temperature evaluated from the magnetic and magnetotransport data is discussed in terms of quantum MIT scenario recently proposed for this low carrier density system.
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Authors: W. Westerburg, D. Reisinger, Gerhard Jakob
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Authors: Bénédicte Vertruyen, Rudi Cloots, André Rulmont, S. Dorbolo, P. Vanderbemden, Marcel Ausloos
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Authors: A. Huda, S.A. Halim, K.P. Lim, O.J. Lee, S. Elias, A.A. Sidek, Z. Hishamuddin
Abstract: Polycrystalline samples of La0.67Ba0.33(Mn1-xRux)O3 with x = 0, 0.05, 0.1, 0.15 and 0.2 have been prepared using solid state reaction. The effects of doping of Ru at Mn site on La-Ba-Mn- O ceramics, the characteristics and magnetotransport properties of CMR materials are investigated. The magnetoresistance (MR) effect is measured using the four point probe technique. The magnetoresistance defined as MR% = (Ro – RH)/RH x 100% was measured at a magnetic field of H ≤ 1T at 90K, 100K, 150K, 200K, 250K, 270K and 300K for the sample of doping x = 0, 0.05, 0.1, 0.15 and 0.2. Overall, MR drops slowly when temperature rises. All doping concentration gives small variation range (~2.7% to ~26.78%). The electrical property has determined by using standard four-point probe resistivity measurement in a temperature range of 30 K to 300 K. Metalinsulator transition temperature (Tp) shifted to lower temperatures as Ru doping is increased. In this paper the structural pattern and microstructure property have investigated via XRD. XRD patterns show that these systems are in orthorhombic distorted perovskite structures.
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Authors: Siau Wei Ng, Kean Pah Lim, S.A. Halim, Hassan Jumiah, Albert H.M. Gan, Hui Wei Chin, Kuen Hou Cheong
Abstract: We have investigated the structural, microstructure and electrical transport properties of nanosized Pr0.85Na0.15MnO3 (PNMO) synthesized by sol-gel technique and sinter from 600°C to 1000°C. The grain size increases from 67 nm (S600) up to 284 nm (S1000) due to the grain growth during heat treatment. XRD showed that single phase orthorhombic crystal structure of PNMO is fully forms started at 600°C. The resistivity decreased with the increased of grain size and crystallite size due to the reduction of grain boundary effect (dead magnetic layer) which improved their grain conductivity.All samples showed semiconductor behavior where their metal insulator transition temperatures (TMIT) were estimated to be lower than 80K.
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Authors: Kai Yap Pan, Abdul H. Shaari, Soo Kien Chen, Kean Pah Lim, Manizheh Navasery, Mohd Mustafa Awang Kechik
Abstract: The influence of sintering temperature on structural, microstructure and transports properties of La0.7Sr0.3MnO3 (LSMO) prepared via sol-gel techniques is introduced. Sintering temperature of LSMO varied from 650°C to 950°C with the interval of 100°C. All samples show single phase structure with hexagonal setting. Refinement was done on the XRD data obtained. Microstructure investigation displayed an increment in average grain size of LSMO due to the grain growth promotion as the sintering temperature increased. Magnetization of all samples was enhanced by the grain growth promotion. Resistivity experienced a reduction trend and Tp shifted to higher temperature as the sintering temperature increased. All sintered LSMO exhibit LFMR effect at low applied field and low temperature.
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