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2. Tunneling of the Mn12-acetate spin cluster

Author

bao, Wei, Robinson, R. A., Friedman, J. R., Casalta, H., Rumberger, E., and Hendrickson, D. N.

Subjects
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

The term in spin Hamiltonian, which determines the quantum tunneling rate in Mn12, is measured with neutron scattering. It is much smaller than previously reported values. This may imply that other mechanisms such as hyperfine fields may be more important in driving the tunneling., Comment: 1 page, 1 figure, comment to Phys Rev Letter

Published
2000

3. Mesoscopic and Microscopic Phase Segregation in Manganese Perovskites

Author

Radaelli, P. G., Ibberson, R. M., Argyriou, D. N., Casalta, H., Andersen, K. H., Cheong, S. -W., and Mitchell, J. F.

Subjects
Condensed Matter - Materials Science, Condensed Matter - Strongly Correlated Electrons
Abstract

Mesoscopic (500-2000 Angstrom) and microscopic (5-20 Angstrom) phase segregation with temperature and magnetic field was studied in the model manganite Pr0.7Ca0.3MnO3 by high-resolution neutron diffraction and inelastic neutron scattering. Intra-granular strain-driven mesoscopic segregation between two insulating phases, one of which is charge ordered (CO), sets in below the CO temperature in zero field. The CO phase orders antiferromagnetically, while the other insulating phase shows spin-glass behavior. After field-induced metallization, the CO phase coexists with a ferromagnetic metallic phase., Comment: 4 figures

Published
2000
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4. Low energy magnetic excitations of the Mn_{12}-acetate spin cluster observed by neutron scattering

Author

Mirebeau, I., Hennion, M., Casalta, H., Andres, H., Güdel, H. U., Irodova, A. V., and Caneschi, A.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

We performed high resolution diffraction and inelastic neutron scattering measurements of Mn_{12}-acetate. Using a very high energy resolution, we could separate the energy levels corresponding to the splitting of the lowest S multiplet. Data were analyzed within a single spin model (S=10 ground state), using a spin Hamiltonian with parameters up to 4^{th} order. The non regular spacing of the transition energies unambiguously shows the presence of high order terms in the anisotropy (D= -0.457(2) cm^{-1}, B_4^0 = -2.33(4) 10^{-5}cm^{-1}). The relative intensity of the lowest energy peaks is very sensitive to the small transverse term, supposed to be mainly responsible for quantum tunneling. This allows an accurate determination of this term in zero magnetic field (B_4^4 = \pm 3.0(5) 10^{-5} cm^{-1}). The neutron results are discussed in view of recent experiments and theories., Comment: 4 pages ? 3 figures, submitted to Physical Review Letter

Published
1999
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5. Superexchange coupling and spin susceptibility spectral weight in undoped monolayer cuprates

Author

Bourges, P., Casalta, H., Ivanov, A. S., and Petitgrand, D.

Subjects
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Superconductivity
Abstract

A systematic inelastic neutron scattering study of the superexchange interaction in three different undoped monolayer cuprates (La_2CuO_4, Nd_2CuO_4 and Pr_2CuO_4) has been performed using conventional triple axis technique. We deduce the in-plane antiferromagnetic (AF) superexchange coupling $J$ which actually presents no simple relation versus crystallographic parameters. The absolute spectral weight of the spin susceptibility has been obtained and it is found to be smaller than expected even when quantum corrections of the AF ground state are taken into account., Comment: 13 pages, 1 table, 3 figures

Published
1997
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6. Dynamics of Frustrated Magnetic Moments in Antiferromagnetically Ordered TbNiAl Probed by Spin Echo and Time-of-Flight Spectroscopy

Author

Ehlers, G., Casalta, H., Lechner, R. E., Maletta, H., Beig, R., editor, Englert, B. -G., editor, Frisch, U., editor, Hänggi, P., editor, Hepp, K., editor, Hillebrandt, W., editor, Imboden, D., editor, Jaffe, R. L., editor, Lipowsky, R., editor, v. Löhneysen, H., editor, Ojima, I., editor, Sornette, D., editor, Theisen, S., editor, Weise, W., editor, Wess, J., editor, Zittartz, J., editor, Mezei, Ferenc, editor, Pappas, Catherine, editor, and Gutberlet, Thomas, editor

Published
2003
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14. Magnetic ordering in PrBa2Cu3-yAlyO6+x

Author

Longmore, A, Boothroyd, AT, Changkang, C, Yongle, H, Nutley, MP, Andersen, NH, Casalta, H, Schleger, P, and Christensen, AN

Published
2016

22. Phase segregation in manganese perovskites

Author

Radaelli, P. O., Argyriou, D. N., Cox, D. E., Capogna, L., Casalta, H., Ken Andersen, Cheong, S. -W, Mitche, J. F., and Marezio, M.

Subjects
Condensed Matter::Materials Science, Condensed Matter::Strongly Correlated Electrons
Abstract

The structural, magnetic and transport phase diagrams of the manganese perovskites (A 1-xA' xMnO 3) are characterized by several phenomena, including high-temperature polaronic behavior, charge-orbital and magnetic ordering and colossal magnetoresistance (CMR). These properties can be tuned by changing the doping level, the electronic bandwidth, and the A-site disorder. To demonstrate this, the recent x-ray synchrotron and neutron diffraction data on the crystallographic and magnetic modulation in La 0.33Ca 0.67MnO 3 are presented.

Published
1999

25. Random-field structural transition in $YBa_2Cu_3O_{6.55}$

Author

Schleger, P., Hadfield, R. A., Casalta, H., Andersen, N. H., Poulsen, H. F., von Zimmermann, M., Schneider, J. R., Liang, R., Dosanjh, P., and Hardy, W. N.

Subjects
ddc:550
Abstract

Physical review letters 74, 1446-1449 (1995). doi:10.1103/PhysRevLett.74.1446, Published by APS, College Park, Md.

Published
1995
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48. Magnetic ordering inPrBa2Cu3−yAlyO6+x

Author

Longmore, A., primary, Boothroyd, A. T., additional, Changkang, Chen, additional, Yongle, Hu, additional, Nutley, M. P., additional, Andersen, N. H., additional, Casalta, H., additional, Schleger, P., additional, and Christensen, A. N., additional

Published
1996
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