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  • 1
    Digitale Medien
    Digitale Medien
    Enhancement of spin correlations in ZnTe/MnTe superlattices by Cl doping (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6460-6462 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The effect of adding Cl impurity on the long-range antiferromagnetic coupling in [ZnTe|MnTe] magnetic semiconductor superlattices has been investigated by neutron diffraction. Superlattices consisting of five atomic planes of ZnTe alternated with ten atomic planes of MnTe[(ZnTe)5|(MnTe)10] have been prepared by molecular-beam epitaxy both with and without Cl added to the MnTe and/or ZnTe layers during deposition. This was motivated by the fact that Cl can form either shallow or deep donor levels in II–VI semiconductors, and that such electronic states can serve to modify magnetic interlayer exchange. Unchlorinated samples showed magnetic correlation lengths of around 225 Å ((approximate)5 bilayers) at low temperatures, and the addition of Cl increased the correlation length at 15 K by nearly a factor of 2 to approximately 450 Å. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.372738
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  • 2
    Digitale Medien
    Digitale Medien
    Spin dynamics and absence of a central peak anomaly in La0.67Ca0.33MnO3 (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 5813-5815 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Low-angle inelastic neutron scattering was used to study the temperature and wave vector dependence of the spin waves in La0.67Ca0.33MnO3 perovskite-based colossal magnetoresistance material. At low q the spin waves show Heisenberg ferromagnetic dispersion (E=Dq2+Δ) where D is the spin stiffness, q is the wave vector, and Δ is the energy gap. However, the temperature renormalization of the spin stiffness D is anomalous, and as T increases toward Tc, D does not show the expected power law collapse, but rather exhibits a sudden sharp drop suggestive of a first-order phase transition. Detailed neutron measurements of the order parameter in zero applied field showed a similar first-order-like transition. However, no temperature hysteresis was observed in either D or in the magnetization. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.372531
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  • 3
    Digitale Medien
    Digitale Medien
    Concurrent Nd and Mn spin excitations in Nd0.6Sr0.4MnO3 (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5564-5566 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The spin dynamics of Nd0.6Sr0.4MnO3 have been determined along [qqq], [qq0], and [00q] propagation directions using inelastic neutron scattering. At T=13 K, the low-q Mn–Mn mode energies varied quadratically with wave vector q, but exhibited marked softening on approach to the zone boundaries when compared with a Heisenberg nearest-neighbor exchange calculation. At the larger q's the modes also show evidence of increasing spin wave energy width. The temperature dependence of the spin wave stiffness parameter D was measured up to Tc=273 K and showed conventional behavior. The 0 K value of D=150 meV Å2 yields D(0)/kTc=6.3. No anomalous E=0 central mode intensity was observed on approach to Tc. At low T additional modes were observed and are ascribed to Nd–Mn exchange interactions. These modes have q=0 spin wave gap of 2.1 meV compared to 1.1 meV for the Mn–Mn excitations.© 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.369896
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  • 4
    Digitale Medien
    Digitale Medien
    Anomalous temperature dependence of interlayer coupling in Fe/Si multilayers (abstract) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4775-4775 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The magnetic coupling of the Fe layers in Fe/Si multilayers strongly depends on the morphology of the iron-silicide interlayer that forms during deposition. Antiferromagnetic interlayer coupling is only observed in Fe/Si multilayers with crystalline interlayers in the CsCl structure. Recently, it has been shown that single layers of Fe–Si in the CsCl structure can be grown epitaxially on Si over a range of stoichiometries. FeSi films are reported to be Kondo insulators below 50 K. We find evidence of a magnetic phase transition in antiferromagnetically coupled Fe/Si multilayers. Ms measured in a constant applied field of 50 kOe shows T3/2 behavior down to 10 K. However, M(T) at a lower constant field peaks around 50 K and decreases at lower temperature, indicating enhanced antiferromagnetic coupling or a phase transition. The remanent magnetization increases monotonically with decreasing temperature and has been explained by invoking thermally activated coupling. However, the saturation field also increases with decreasing temperature, indicating a stronger antiferromagnetic interaction. We explore the suggestion that the interlayer coupling is biquadratic in nature. Polarized neutron reflectometry has also been used to get a clearer picture of the complicated magnetic behavior of this multilayer system. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.361861
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  • 5
    Digitale Medien
    Digitale Medien
    Magnetic properties of (11¯02) Dy/Y superlattices : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4779-4781 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Epitaxial (11¯02) Dy/Y rare earth superlattices and a thick (11¯02) Dy film, grown on sapphire with Y/Ta buffer layers, have been prepared by molecular beam epitaxy. Neutron diffraction and SQUID magnetization measurements on a single 200 nm thick (11¯02) Dy layer showed nearly bulk behavior. However, for the (11¯02) Dy/Y superlattices we found different magnetic behavior depending on the relative Dy to Y-layer thickness. The superlattices exhibit both ferromagnetic and helical phases, but with the Néel and Curie temperatures significantly different from bulk Dy. These results differ from previous findings in Dy/Y superlattices grown along [0001]. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.361669
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  • 6
    Digitale Medien
    Digitale Medien
    Structural, field, and temperature dependence of noncollinear magnetic coupling in Fe/Cr(001) superlattices (abstract) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4782-4782 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Utilizing the magneto-optic Kerr effect (MOKE) in conjunction with x-ray and neutron reflectometry (NR) and diffraction, we have studied the magnetic coupling of Fe/Cr(001) superlattices grown at room temperature and 250 °C. Only the samples grown at elevated temperature exhibit noncollinear coupling of 5.0 nm Fe layers across 1.7 nm Cr interlayers. The noncollinear samples feature a less-disordered in-plane interfacial structure than those grown at room temperature. Using x-ray diffuse reflectivity, we have measured a length scale of 10 nm for these in-plane features. We have also observed, via NR, a remanent noncollinear coupling angle of 50° and, via MOKE and NR, a gradual approach to saturation at upwards of 7 kOe. These features can be explained qualitatively by the proximity magnetism model of Slonczewski. We will compare the predictions of both the proximity and bilinear/biquadratic models with our data and present the results of ongoing neutron measurements of the temperature dependence of the coupling. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.361670
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  • 7
    Digitale Medien
    Digitale Medien
    Temperature dependence of noncollinear magnetic coupling in Fe/Cr(001) superlattices : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 3765-3766 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Using polarized-neutron reflectivity, we have measured the temperature dependence of the noncollinear magnetic coupling of ferromagnetic iron across chromium interlayers in two superlattice samples. The first sample, (52 Å Fe/17 Å Cr)9, exhibits a room temperature remanent magnetic structure consisting of successive Fe layer moments aligned at 50° relative to each other. This magnetic structure remains unchanged upon cooling the sample to 42 K. In contrast, a superlattice with a thicker Cr interlayer, [44 Å Fe/88 Å Cr]30, passes in a 20 K-wide transition centered on TN=240 K from a room temperature state with Fe moments aligned at 90° to an uncoupled state. The formation of the incommensurate Cr spin density wave state below TN suppresses the interlayer coupling. The thinner Cr interlayers do not undergo a transition to this bulk structure, hence exhibit no suppression of coupling. In both samples, the coupling strength decreases for temperatures at and above room temperature. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.365501
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  • 8
    Digitale Medien
    Digitale Medien
    Long wavelength spin dynamics in La0.53Ca0.47MnO3 : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 7339-7341 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The magnetic structure and dynamics in the colossal magnetoresistance (CMR) class perovskite La0.53Ca0.47MnO3 have been studied by elastic and inelastic neutron scattering. This composition is near the 0.5 Ca transition from a metallic ferromagnet to an insulating antiferromagnet. Powder neutron diffraction on these samples showed coexisting ferromagnetic and antiferromagnetic phases at low temperature and a splitting of the lattice parameters of the antiferromagnetic phase near TN, reflecting the onset of the charge ordered state. Inelastic scattering measurements of the ferromagnetic excitations exhibited well-defined spin waves of resolution width below Tc. The spin waves exhibited conventional Heisenberg behavior with dispersion of the form E=Dq2+Δ with spin stiffness D(T=0 K)(approximate)135 meV Å2 and an energy gap Δ(approximate)0.1 meV. The value of the spin wave stiffness D is similar to that found for other ferromagnetic perovskite materials, and it renormalized with temperature in a manner consistent with the magnetization. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.367633
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  • 9
    Digitale Medien
    Digitale Medien
    Purification of wood Rosin1 (1930)
    s.l. : American Chemical Society
    Industrial & engineering chemistry 22 (1930), S. 446-448 
    Details
    ISSN: 1520-5045
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/ie50245a008
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  • 10
    Digitale Medien
    Digitale Medien
    Exchange coupling in [Dy||Er] metallic superlattices : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6477-6479 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Magnetic exchange coupling in metallic superlattices of [Dy||Er], grown by molecular-beam epitaxy, has been examined by neutron diffraction. In a superlattice of 65-A(ring) layers of Dy and 55-A(ring) layers of Er, distinct ordering temperatures were observed for the Dy and Er layers. Basal plane helical ordering of the Dy layers was initiated at temperatures close to TN for bulk Dy (178 K) with a long-range interaction, preserving both phase and chirality, mediated through the Er layers. At a temperature near 70 K, the helical coupling of the Dy spins is replaced by an antiferromagnetic coupling of adjacent ferromagnetically ordered Dy layers coexisting with a remanent helical order. At a temperature well below TN of bulk Er, c-axis ordering of the Er spins occurs in the superlattice, and in measurements at 10 K there is evidence of basal plane moment ordering in the Er.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.357035
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