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  • 1
    Electronic Resource
    Electronic Resource
    Magnetic transitions in Pr2NiO4 single crystal : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6329-6331 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic properties of a stoichiometric Pr2NiO4 single crystal have been examined by means of the temperature dependence of the complex ac susceptibility and the isothermal magnetization in fields up to 200 kOe at T=4.2 K. Three separate phases have been identified and their anisotropic character has been analyzed. A collinear antiferromagnetic phase appears first between TN = 325 K and Tc1 = 115 K, where the Pr ions are polarized by an internal magnetic field. At Tc1 a first modification of the magnetic structure occurs in parallel with a structural phase transition (Bmab to P42/ncm). This magnetic transition has a first-order character and involves both the out-of-plane and the in-plane spin components (magnetic modes gx and gxcyfz, respectively). A second magnetic transition having also a first-order character is also clearly identified at Tc2 = 90 K which corresponds to a spin reorientation process (gxcyfz to cxgyaz magnetic modes). It should be noted as well that the out-of-phase component of χac shows a peak around 30 K which reflects the coexistence of both magnetic configurations in a wide temperature interval. Finally, two field-induced transitions have been observed at 4.2 K when the field is directed along the c axis. We propose that the high-field anomaly arises from a metamagnetic transition of the weak ferromagnetic component, similarly to La2CuO4.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349958
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  • 2
    Electronic Resource
    Electronic Resource
    Spin glass transition in BaCo6Ti6O19 : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6172-6174 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thermomagnetic ac and dc measurements were carried out on polycrystalline BaCo6Ti6O19. The system shows all the characteristic signatures of the spin glass syndrome. dc magnetic susceptibility displays a sharp peak at Tf = 13.6 K and below this temperature a clear onset of irreversibility between the zero field cooled and field cooled (ZFC–FC)processes is observed. The real part of the ac susceptibility shows also a sharp peak at Tf which strongly depends on the frequency of the ac magnetic field. The dynamic critical behavior of the system is studied by analyzing the imaginary part of the ac susceptibility in the scope of two models: the activated dynamic scaling and the equilibrium phase transition scaling. The best data collapsing is obtained assuming that a true phase transition occurs at the freezing temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350034
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  • 3
    Electronic Resource
    Electronic Resource
    Spin glass-like behavior in Fe-doped Bi4Sr8Cu5O19+x insulating perovskite : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6184-6186 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polycrystalline samples of the tubular phase Bi4Sr8Cu5O19+x with Fe ions substituting the Cu positions have been prepared up to a maximum content of 2 Fe ions per unit formula. The electrical and magnetic properties of these oxides have been examined and it is shown that they are insulating and present a complex magnetic behavior. It is found that the Fe ions have a localized magnetic moment displaying a Curie–Weiss law at high temperatures while below T≈100 K antiferromagnetic correlations are detected. From the evaluation of the effective paramagnetic moment and its composition dependence it is deduced that Fe doping induces a paramagnetic moment in some Cu ions which then contribute also to the temperature dependent paramagnetism. Finally, at lower temperatures (T〈25 K) a susceptibility peak is observed signaling a freezing of the magnetic moments. We suggest a spin-glass behavior associated either to a clustering of Fe ions or to the development of correlated domains interacting through the strongly correlated copper ions. We point out that the weak sensitivity of the resistivity on the Fe concentration gives further support to the hypothesis of some Fe clustering within the tubular crystal structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350012
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  • 4
    Electronic Resource
    Electronic Resource
    Tunable epitaxial growth of magnetoresistive La2/3Sr1/3MnO3 thin films (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4800-4802 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the growth of epitaxial La2/3Sr1/3MnO3 thin films on buffered Si(001) substrates. We show that a suitable choice of the buffer heterostructure allows one to obtain epitaxial (00h), (0hh), and (hhh) manganite thin films. The magnetotransport properties are investigated and we have found that the low-field magnetoresistance is directly related to the width of the normal-to-plane rocking curves, irrespective of the film orientation. The magnetic anisotropy of these films has also been determined. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370486
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  • 5
    Electronic Resource
    Electronic Resource
    Paramagnetic susceptibility and ferromagnetism in Sr2FeMoO6 perovskites (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7684-7686 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article, we report a detailed study of the paramagnetic susceptibility χ of Sr2FeMoO6 ceramic samples prepared under various conditions. We show that χ−1(T,H) has a rather unconventional behavior in the 800 K〉T〉TC((approximate)400 K) temperature range, namely, a field-dependent χ−1(T) slope which is also sensitive to the synthesis conditions. Detailed analysis and comparison of samples allow us to conclude that this behavior is nonintrinsic but rather reflects the sample quality. We quantitatively show that small amounts of ferromagnetic impurities (〈0.1%) can account for the observed behavior. In spite of this, we demonstrate that the dominant magnetic interactions in this system are ferromagnetic, thus strongly supporting a double-exchange mechanism for magnetic interactions. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1358349
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  • 6
    Electronic Resource
    Electronic Resource
    Transport and magnetic properties of Tl2Mn2−xRuxO7 diluted system (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5405-5407 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic and transport properties of Tl2Mn2−xRuxO7 pyrochlores are analyzed as a function of the substitution rate (0≤x≤2). For x≤0.2, the system exhibits colossal magnetoresistance (CMR) and ferromagnetic ordering. For higher doping rates CMR is completely washed out and the transport properties mimics that of the Tl2Ru2O7 pure compound with a semiconductor-to-metal transition at a temperature that decreases as x increases. The magnetic frustration progressively increases signalling the increase of antiferromagnetic interactions and the geometrical frustration intrinsic to the pyrochlore structure. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369992
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  • 7
    Electronic Resource
    Electronic Resource
    Thickness dependence of surface roughness and transport properties of La2/3Ca1/3MnO3 epitaxial thin films (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6686-6688 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this work, we report on the impact of distinct growth parameters that affect the roughness and surface morphology of La2/3Ca1/3MnO3 epitaxial thin films grown by rf sputtering, namely, the film thickness and the deposition temperature. Data for films with thicknesses ranging from 2.4 to 108 nm will be presented. A correlation with transport measurements is also reported: whereas films thicker than 6 nm show the typical metal-to-insulator transition, the thinner film is insulating. The resistivity is strongly enhanced when decreasing film thickness. Nuclear magnetic resonance measurements have been used to monitor the relative concentration of the localized Mn4+ and delocalized Mn3+/4+ states. It is found that the relative intensity of the delocalized Mn3+/4+ configuration (I3+/4+) progressively lowers when reducing film thickness. Of significance could be the observation that I3+/4+ remains finite for the thicknesses corresponding to insulating films, thus suggesting that an electrically inhomogeneous state is formed in a region close to the interface with the substrate. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1359231
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  • 8
    Electronic Resource
    Electronic Resource
    Alternating current susceptibility study of the low doped regime of La1−xSrxMnO3 perovskites (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6633-6635 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dynamic response of La1−xSrxMnO3 perovskites has been studied in the low doped regime (x≤0.14). The frequency dependence of the ac susceptibility gives clear indications in favor of the existence of electronic phase separation not only in the O″ phase but also at temperatures between the ferromagnetic transition temperature TC, and the O′–O″ structural transition occurring at TFI. The influence of the Jahn–Teller distortion on the magnetic susceptibility is also detected as a drop in the magnetic susceptibility on crossing down the O–O′ structural transition, while a jump occurs at O′–O″ transition. A close similarity, both structural and magnetic, between the O and O″ phase is strongly suggested by the experimental results. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1357138
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  • 9
    Electronic Resource
    Electronic Resource
    Plastic deformation in high critical current melt-textured YBa2Cu3O7 (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 5515-5517 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of high-temperature creep under different conditions in melt-textured YBa2Cu3O7–Y2BaCuO5 composites, with high critical currents before deformation, is investigated. Transmission electron microscopy studies show that the low-temperature oxygenation process causes a strong modification of the as-deformed microstructure and leads to a clear degradation of the superconducting performances. This behavior of the superconducting properties is well correlated with the formation of extended planar defects such as large stacking faults and microcracks that severely diminish the vortex cutting length, thus enhancing the thermal activation effects on the critical currents and the irreversibility line. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363484
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  • 10
    Electronic Resource
    Electronic Resource
    Magnetic properties of colossal magnetoresistive manganese oxides : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5182-5184 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of isovalent substitution into the lanthanide sites in La1−xYxCa0.30MnO3−δ oxides is presented. We report on the electrical and magnetic properties of these materials for x=0–0.25. We have found that the ferromagnetic ordering temperature decreases and the cusp of the resistivity occurring at this temperature increases when the smaller lanthanide Y is introduced into the lattice. We will provide evidence that a key signature of the magnetic properties of these oxides is the presence of an unusual long tail in the magnetization versus temperature curves M(T), extending up to 3TM and which is very sensitive to the applied magnetic field and becomes increasingly important with the concentration of Y in the lattice. These features signal a strong polarizability of the spin clouds in these materials as our Mössbauer experiments will clearly demonstrate. Finally, we will show that the magnetoresistance of these compounds can be well-described in terms of a spin-disorder scattering mechanism. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361332
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