oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Depth profile of the ferromagnetic order in a YBa$_2$Cu$_3$O$_7$ / La$_{2/3}$Ca$_{1/3}$MnO$_3$ superlattice on a LSAT substrate: a polarized neutron reflectometry study  [PDF]
M. A. Uribe-Laverde,D. K. Satapathy,I. Marozau,V. K. Malik,S. Das,K. Sen,J. Stahn,A. Rühm,J. -H. Kim,T. Keller,A. Devishvili,B. P. Toperverg,C. Bernhard
Physics , 2012, DOI: 10.1103/PhysRevB.87.115105
Abstract: Using polarized neutron reflectometry (PNR) we have investigated a YBa2Cu3O7(10nm)/La2/3Ca1/3MnO3(9nm)]10 (YBCO/LCMO) superlattice grown by pulsed laser deposition on a La0.3Sr0.7Al0.65Ta0.35O3 (LSAT) substrate. Due to the high structural quality of the superlattice and the substrate, the specular reflectivity signal extends with a high signal-to-background ratio beyond the fourth order superlattice Bragg peak. This allows us to obtain more detailed and reliable information about the magnetic depth profile than in previous PNR studies on similar superlattices that were partially impeded by problems related to the low temperature structural transitions of the SrTiO3 substrates. In agreement with the previous reports, our PNR data reveal a strong magnetic proximity effect showing that the depth profile of the magnetic potential differs significantly from the one of the nuclear potential that is given by the YBCO and LCMO layer thickness. We present fits of the PNR data using different simple block-like models for which either a ferromagnetic moment is induced on the YBCO side of the interfaces or the ferromagnetic order is suppressed on the LCMO side. We show that a good agreement with the PNR data and with the average magnetization as obtained from dc magnetization data can only be obtained with the latter model where a so-called depleted layer with a strongly suppressed ferromagnetic moment develops on the LCMO side of the interfaces. The models with an induced ferromagnetic moment on the YBCO side fail to reproduce the details of the higher order superlattice Bragg peaks and yield a wrong magnitude of the average magnetization. We also show that the PNR data are still consistent with the small, ferromagnetic Cu moment of 0.25muB that was previously identified with x-ray magnetic circular dichroism and x-ray resonant magnetic reflectometry measurements on the same superlattice.
Superconducting and normal-state interlayer-exchange-coupling in La$_{0.67}$Sr$_{0.33}$MnO${3}$-YBa$_{2}$Cu$_{3}$O$_{7}-La$_{0.67}$Sr$_{0.33}$ MnO${3}$ epitaxial trilayers  [PDF]
K. Senapati,R. C. Budhani
Physics , 2005, DOI: 10.1103/PhysRevB.71.224507
Abstract: The issue of interlayer exchange coupling in magnetic multilayers with superconducting (SC) spacer is addressed in La$_{0.67}$Sr$_{0.33}$MnO$_{3}$ (LSMO) - YBa$_{2}$Cu$_{3}$O$_{7}$ (YBCO) - La$_{0.67}$Sr$_{0.33}$MnO$_{3}$ (LSMO) epitaxial trilayers through resistivity, ac-susceptibility and magnetization measurements. The ferromagnetic (FM) LSMO layers possessing in-plane magnetization suppress the critical temperature (T$_{c})$ of the c-axis oriented YBCO thin film spacer. The superconducting order, however, survives even in very thin layers (thickness d$_{Y} \sim $ 50 {\AA}, $\sim $ 4 unit cells) at T $<$ 25 K. A predominantly antiferromagnetic (AF) exchange coupling between the moments of the LSMO layers at fields $<$ 200 Oe is seen in the normal as well as the superconducting states of the YBCO spacer. The exchange energy J$_{1}$ ($\sim $ 0.08 erg/cm$^{2}$ at 150 K for d$_{Y}$ = 75 {\AA}) grows on cooling down to T$_{c}$, followed by truncation of this growth on entering the superconducting state. The coupling energy J$_{1}$ at a fixed temperature drops exponentially with the thickness of the YBCO layer. The temperature and d$_{Y}$ dependencies of this primarily non-oscillatory J$_{1}$ are consistent with the coupling theories for systems in which transport is controlled by tunneling. The truncation of the monotonic T dependence of J$_{1}$ below T$_{c}$ suggests inhibition of single electron tunneling across the CuO$_{2}$ planes as the in-plane gap parameter acquires a non-zero value.
Appearance of an inhomogeneous superconducting state in La{0.67}Sr{0.33}MnO{3}-YBa{2}Cu{3}O{7}-La{0.67}Sr{0.33}MnO{3} trilayers  [PDF]
K. senapati,R. C. Budhani
Physics , 2005,
Abstract: An experimental study of proximity effect in La{0.67}Sr{0.33}MnO3 - YBa2Cu3O7 - La{0.67}Sr{0.33}MnO3 trilayers is reported. Transport measurements on these samples show clear oscillations in critical current (I_c) as the thickness of La{0.67}Sr{0.33}MnO3 layers (d_F) is scanned from ~ 50 A to ~ 1100 A. In the light of existing theories of ferromagnet-superconductor (FM-SC) heterostructures, this observation suggests a long range proximity effect in the manganite, modulated by it's weak exchange energy (~ 2 meV). The observed modulation of the magnetic coupling between the ferromagnetic LSMO layers as a function of d_F, also suggests an oscillatory behavior of the SC order parameter near the FM-SC interface.
Magnetotransport properties of La0.67Ca0.33MnO3/La0.67Sr0.33MnO3 bilayers
Magnetotransport properties of La0.67Ca0.33MnO3//La0.67Sr0.33MnO3 bilayers

Feng Jia-Feng,Zhao Kun,Huang Yan-Hong,Zhao Jian-Gao,Han Xiu-Feng,Zhan Wen-Shan,Wong Hong-Kuen,
丰家峰
,赵 昆,黄延红,赵见高,韩秀峰,詹文山,黄康权

中国物理 B , 2005,
Abstract: The perovskite bilayers La0.67Ca0.33MnO3 (LCMO) (100nm) / La0.67Sr0.33MnO3(LSMO) (100 nm) and LSMO (100 nm) / LCMO (100 nm) are fabricated by a facing-target sputtering technique. Their transport and magnetic properties are investigated. It is found that the transport properties between them are different obviously due to distinguishable structures, and the different lattice strains in both films result in the difference of metal-to-insulator transition. Only single-step magnetization loop appears in our bilayers from 5K to 320K, and the coercive force of LSMO/LCMO varies irregularly with a minimum \sim 2387A/m which is lower than that of LCMO and LSMO single layer films. The behaviour is explained by some magnetic coupling.
Polarity Switchable Photovoltages in Miscut La0.67Ca0.33MnO3 Films
J. Wang,H. Ni,K. Zhao,Y.-C. Kong,H. K. Wong,S. X. Zhong
International Journal of Photoenergy , 2012, DOI: 10.1155/2012/547591
Abstract: We report the transient laser-induced anomalous photovoltaic effect in the La0.67Ca0.33MnO3 film grown on miscut LaSrAlO4 (001) substrate under 248 nm pulsed laser irradiation at ambient temperature without any applied bias. A photovoltaic pulse signal was observed when the La0.67Ca0.33MnO3 film was irradiated directly, and the signal polarity was reversed when the sample was irradiated through the LaSrAlO4 substrate, while the signal recorded between the two electrodes on the surface of LaSrAlO4 was not reversed when the sample was irradiated through La0.67Ca0.33MnO3 film rather than at the surface of LaSrAlO4. The switchable signal polarity provides a potential application of miscut manganite films as optical components. A possible mechanism is introduced to explain the experiment results.
Preisach analysis of La0.67Pb0.33MnO3
La0.67Pb0.33MnO3的Preisach分析

Xiao Chun-Tao,Cao Xian-Sheng,
肖春涛
,曹先胜

物理学报 , 2004,
Abstract: 测量了居里点TC=360K的钙钛矿La0.67Pb0.33MnO3在2K
Giant enhancement of room temperature magnetoresistance in La_{0.67}Sr_{0.33}MnO_{3}/Nd_{0.67}Sr_{0.33}MnO_{3} multilayers  [PDF]
Soumik Mukhopadhyay,I. Das
Physics , 2005, DOI: 10.1063/1.2166200
Abstract: The metal-insulator transition temperature in CMR manganites has been altered and brought close to the room temperature by preparing La$_{0.67}$Sr$_{0.33}$MnO$_{3}$ (LSMO)/ Nd$_{0.67}$Sr$_{0.33}$MnO$_{3}$ (NSMO) multilayers with ultra thin individual layers of LSMO and NSMO. The LSMO/NSMO multilayers with ultra thin individual layers of thickness of about $10\AA$ exhibits 150% magnetoresistance at 270 K whereas LSMO/NSMO multilayers with moderate individual layer thickness of about $40\AA$ each exhibits a mere 15% magnetoresistance at the same temperature. We have shown that the reduction in thickness of the individual layers leads to increased spin fluctuation which results in the enhancement of magnetoresistance.
Electron magnetic resonance studies of nanomanganite Nd0.67Sr0.33MnO3  [PDF]
S. S. Rao,Subhasis Sarangi,G. Venkataiah,Venu Gopala Reddy,S. V. Bhat
Physics , 2005,
Abstract: Nd_0.67Sr_0.33MnO_3 nanoparticles with the grain size of about 30 nm are prepared by sol-gel method.These nanopowders are annealed at four different temperatures viz. 800 oC, 900 oC, 1000 oC and 1100 oC to study the effect of particle size on magnetic, transport and electron magnetic resonance (EMR) spectral parameters. The samples are characterized by XRD, SEM, EDAX and TEM. The ac susceptibility experiments show that as the particle size increases the ferromagnetic to paramagnetic transition temperature (Tc) decreases. The metal-insulator transition temperature also changes with the particle size as revealed by resistivity measurements. EMR spectra of the nanopowders are recorded from room temperature down to 4K using an X-band EPR spectrometer. the spectra could be fitted using two broad-Gaussian lineshapes below Tc and suggested the ferromagnetic nature of the samples. Above Tc a single Lorenzian fits the signals as expetced for paramagnetic samples. The EMR spectral parameters are found to be different from the bulk (polycrystalline)sample data. The spectral parameters show variation with the particle size. The presence of the two signals in the ferromagnetic phase is attributed to core and shell regions in the nanoparticles. We could estimate the shell thickness from the EMR intensity data as 0.7 - 1 nm which agrees with other measurements.
Microphase separation in Pr0.67Ca0.33MnO3 by small angle neutron scattering  [PDF]
Ch. Simon,S. Mercone,N. Guiblin,C. Martin,A. Brulet
Physics , 2002, DOI: 10.1103/PhysRevLett.89.207202
Abstract: We have evidenced by small angle neutron scattering at low temperature the coexistence of ferromagnetism (F) and antiferromagnetism (AF) in Pr0.67Ca0.33MnO3. The results are compared to those obtained in Pr0.80Ca0.20MnO3 and Pr0.63Ca0.37MnO3, which are F and AF respectively. Quantitative analysis shows that the small angle scattering is not due to a mesoscopic mixing but to a nanoscopic electronic and magnetic ''red cabbage'' structure, in which the ferromagnetic phase exists in form of thin layers in the AF matrix (stripes or 2D ''sheets'').
Magnetic and transport properties of perovskite La0.67Pb0.33MnO3
La0.67Pb0.33MnO3的磁性及输运特性

HKunkel,GWilliams,
肖春涛
,韩立安,薛德胜,赵俊慧,H.Kunkel,G.Williams

物理学报 , 2003,
Abstract: 利用固相反应烧结法制备了La067Pb033MnO3单相多晶样品.研究了其结构、磁性及输运特性.结果表明,样品呈菱面相晶体结构,空间群为R3C,居里温度TC(=353K)非常接近TMI(=360K).在居里温度附近,发生铁磁-顺磁转变,导电特性由金属特征向半导体特征过渡.磁电阻在居里点达到极大值.当H=16T时,磁电阻的极大值为145%;当H=08T时,磁电阻的极大值为9%.输运性质表明,TTMI时
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.