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  • 1
    Electronic Resource
    Electronic Resource
    Magnetic and transport behaviors of La0.5(Sr0.53Ca0.47)0.5MnO3 under pressure, magnetic field, and Fe doping (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3139-3144 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Effects of pressure, magnetic field, and Mn-site doping on the magnetic structure and resistive behavior of La0.5(Sr0.53Ca0.47)0.5Mn1−xFexO3 (0≤x≤0.10) have been experimentally studied. The system experiences two magnetic transitions subsequently with decreasing temperature: a paramagnetic to ferromagnetic transition and a ferromagnetic to antiferromagnetic (AFM) transition. The second magnetic transition coincides with a steep resistivity jump. In addition to reducing the critical temperature for the AFM transition (TN), the incorporation of Fe enhances the ferromagnetic order below TN as demonstrated by the gradual increase of magnetization with the content of Fe. Long-range AFM order is replaced by short-range AFM order when x exceeds 0.03, and disappears completely for x〉0.06. The application of pressure or magnetic field depresses the AFM nature of the compounds, resulting in a downward shift of TN at a rate of ∼7 K/GPa or ∼4 K/T. The most interesting observation of the present study is the greatly enhanced resistivity jump at TN, which increase from 1 to 2 orders, after the sample undergoes a pressurizing and then a pressure relieving process. Although high pressure, magnetic field, and Fe doping produce similar effects on the AFM order, the underlying physics is different. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1446228
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  • 2
    Electronic Resource
    Electronic Resource
    Spin-state transition in La1−xSmxCoO3 perovskites (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 1331-1335 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Structural and magnetic properties of La1−xSmxCoO3 with x=0, 0.02, 0.04, 0.06, 0.08, 0.12, 0.16, and 0.2 have been systematically studied. LaCoO3 exhibits a rhombohedral structure of R3¯C symmetry. The lattice parameters decrease progressively with the incorporation of Sm, and a second orthorhombic phase of Pbnm symmetry appears for x≥0.12. The volume fraction of the orthorhombic phase is a sensitive function of the Sm content in the compounds, and increases from 16% for x=0.12 to 75% for x=0.2. Accordingly, the low-spin-to-high-spin transition of the trivalent Co ions, characterized by a steep rise of the magnetization, shifts to higher temperatures. A molecular field analysis indicates an increased energy gap, from 317 K for x=0 to 500 K for x=0.2, between the low-spin and the high-spin state, implying a stabilization of the low-spin trivalent Co ions by the presence of Sm. The enhanced compressive chemical pressure due to the introduction of Sm is suggested to be responsible for the present observations. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1336521
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  • 3
    Electronic Resource
    Electronic Resource
    Crystal structure and electronic transport property of perovskite manganese oxides with a fixed tolerance factor (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 1900-1902 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structural and electronic transport properties of ABO3-type compounds La2/3−xRxCa1/3MnO3(R=Pr, Nd, Sm, Eu, Gd, Tb, Dy, Y, Er, and Tm) with a fixed tolerance factor of t=0.91137 is studied. Similar structure deformation, characterized by the nearly constant average Mn–O, A–O distances and Mn–O–Mn bond angles, is observed in different compounds. The metal–semiconductor transition shows a strong R dependent feature. The transition temperature decreases monotonously from 187 to 77.6 K as R varies from Tm to Pr, with a corresponding maximum resistivity ranging from 2.34 to 6.17×104 Ω cm. Very different magnetoresistance effects are also observed in this series of compounds. By assuming the presence of inhomogeneous local lattice distortions due to ions with different sizes at A sites and their mismatch with B ions, the lattice effects can be understood qualitatively. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118725
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetism of perovskite manganese oxide La1/3Nd1/3Ca1/3MnO3 (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 4687-4689 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetism of bulk La1/3Nd1/3Ca1/3MnO3 with a magnetoresistance ratio as high as −96% in a field of 0.67 T is investigated. Two shoulders are observed on both thermal magnetization curves and magnetization isotherms. A magnetic inhomogeneity model, i.e., simultaneous occurrence of ferromagnetic La-rich domains and nonferromagnetic Nd-rich domains in the compound, is proposed. The model gives a satisfactory explanation for the experimental results. It is argued that a field-induced magnetic transition occurs in the Nd-rich phase and the coexisting La-rich phase can promote the magnetic transition. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366210
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  • 5
    Electronic Resource
    Electronic Resource
    Oxygen content dependence of the transport property of La2/3Sr1/3CoO3−δ film (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 2831-2835 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Effects of oxygen content on the resistivity of epitaxial (110)La2/3Sr1/3CoO3−δ film have been experimentally studied. The oxygen release, measured by the change of lattice parameter, was controlled by annealing the film at different temperatures in vacuum. Significant oxygen loss can take place at temperature as low as ∼200 °C. A quantitative relation between resistivity ρ and oxygen deficiency δ was established. For δ〈0.07, a linear decrease of the resistive transition temperature with δ was found. The temperature dependence of the low temperature resistivity follows ρ∝T2 for δ〈0.046, and ρ∝exp[(T0/T)1/2] for 0.067〈δ〈0.16. A transition from T1/2 variable-range hopping to T1/4 variable-range hopping takes place for δ〉0.17, which may be a result of the absence of Co4+ which are the nuclei of metallic clusters. Compared to La1−xSrxCoO3 with similar Co4+ content, the resistivity of the La2/3Sr1/3CoO3−δ film is significantly low, which may be the consequence of a larger quantity of Sr in the film. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1390500
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  • 6
    Electronic Resource
    Electronic Resource
    Structural and magnetoresistive properties of La0.7Ca0.3Mn0.96(Al1−xInx)0.04O3 (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 3619-3622 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Structural, magnetic, and transport properties of ABO3-type La0.7Ca0.3Mn0.96(Al1−xInx)0.04O3 are investigated. Different structure deformation from that in the A-site doping, characterized by the synchronous variation of the lattice constants b with c/(square root of 2) versus the content of In in the compounds, is observed. The metal–semiconductor transition shows a strong In content dependence. The transition temperature decreases monotonously from 180.7 to 103.4 K as x varies from 0 to 1, with a corresponding maximum resistivity ranging from 2.9 to 410.8 Ω cm. The magnetoresistive properties of the materials are strongly affected by the size mismatch between A- and B-site ions, and a relation similar to that presented by Hwang et al. [Phys. Rev. Lett. 75, 914 (1995)] is observed though controlling of the tolerance factor, is realized by B-site doping. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369723
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  • 7
    Electronic Resource
    Electronic Resource
    On-axis dc magnetron sputtering of large area high quality YBa2Cu3O7 superconducting thin films (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 348-350 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is demonstrated by our experiment that using the in situ dc magnetron sputtering method, it is possible to prepare high quality YBa2Cu3O7 (YBCO) thin films with substrates facing the region of plasma ring. The effect of oxygen resputtering can be greatly reduced with a high argon-oxygen working gas ratio and a large target to substrate distance. It is shown that high quality YBCO thin films of more than 60 mm in diameter, that is about the same size of the diameter of the YBCO target, can be prepared with this process. The thin films were characterized by x-ray diffractometry, and the critical temperatures were determined by both resistive and ac susceptibility techniques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107933
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  • 8
    Electronic Resource
    Electronic Resource
    Giant magnetoresistance effect in bulk La1/3Nd1/3Ca1/3MnO3 at low field (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 424-426 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A magnetoresistance ratio as high as −96% in a low field of 0.67 T is achieved in bulk La1/3Nd1/3Ca1/3MnO3. The magnetization exhibits a transition from a low moment state to a high moment state with decreasing temperature, accompanied by a thermal hysteresis of the magnetization. The magnetic transition might be an order-order transition and would be responsible for the observed giant magnetoresistance effect in the compound at low field. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118082
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  • 9
    Electronic Resource
    Electronic Resource
    Doping effects arising from Fe and Ge for Mn in La0.7Ca0.3MnO3 (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 2998-3000 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Structural, magnetic, and transport properties of polycrystalline La0.7Ca0.3Mn1−xFexO3 and La0.7Ca0.3Mn1−xGexO3 are experimentally studied. Single-phase samples are obtained in the range x=0–0.12 for Fe, and x=0–0.06 for Ge. There are no appreciable structure changes due to the introduction of Fe and Ge. The Mn-site doping favors a reduced magnetic/resistive transition, at rates of ∼22 K for 1% Fe and ∼28 K for 1% Ge, and an elevated resistivity. No metal–insulator transition occurs when the content of Fe exceeds ∼0.1. The enhanced doping effects in La0.7Ca0.3Mn1−xGexO3 can be ascribed to the reduced hole concentration noting that the presence of Fe and Ge influence the contents of mobile eg electrons and holes in the compounds, respectively. Equivalence of the effects from Fe and Ge doping, respectively, to those due to eg electron and hole trapping and the relation between Mn- and O-site doping are discussed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122656
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  • 10
    Electronic Resource
    Electronic Resource
    Complex magnetic and electronic transport properties of (La,Gd)1−xSrxMnO3+δ perovskites (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 3718-3720 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic and transport properties of (La,Gd)1−xSrxMnO3+δ (x=0.15, 0.2, 0.25, and 0.3) with a fixed tolerance factor t=0.913 are studied. Special attention is paid to the postannealing effects of the compounds. Two magnetic transitions are observed in samples x=0.2 and 0.25 which are single phase in structure according to powder x-ray diffraction. Different effects on the two resulting states are produced by the postannealing. Accompanying the weakening of the state at lower temperature, the magnetic ordering of high-temperature state is enhanced substantially by the introduction of excess oxygen due to annealing the samples in O2. One typical paramagnetic–ferromagnetic transition occurs in samples x=0.15 and 0.3. There is a strong indication that the magnetic states in x=0.15 and 0.3 are, respectively, the developments of the high- and low-temperature states in x=0.2 (or x=0.25). The occurrence of two metal–semiconductor transitions in x=0.15–0.25 and their responses to postannealing suggest magnetic heterogeneity in the compound. By assuming the coexistence of vacancy-rich and vacancy-deficient domains in the compounds, these observations can be understood qualitatively. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120492
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