Now showing items 23-42 of 58

    • Exploiting finite size effects in a novel core/shell microstructure 

      Liu, Zhu; Xia, Guoqiang; Zhu, Frank; Kim, Su; Markovic, Nina; Chien, Chia-Ling; Searson, Peter C. (American Institute of Physics, 2008-03-15)
      Electrodeposition of Ni-Cu alloys at high Cu(II) concentration and large overpotentials results in phase separation with a unique microstructure characterized by features with a copper-rich core and a nickel-rich shell. ...
    • Fermionic spin excitations in two- and three-dimensional antiferromagnets 

      Zhihao, Hao; Tchernyshyov, O. (American Physical Society, 2009-10-30)
      Spin excitations in an ordered Heisenberg magnet are magnons-bosons with spin 1. That may change when frustration and quantum fluctuations suppress the order and restore the spin-rotation symmetry. We show that spin ...
    • Field dependence of magnetic ordering in Kagome-staircase compound Ni3V2O8 

      Kenzelmann, M.; Harris, A.B.; Aharony, A.; Entin-Wohlman, O.; Yildirim, T.; Huang, Q.; Park, S.; Lawes, G.; Broholm, C.; Rogado, N.; Cava, R.J.; Kim, K.H.; Jorge, G.; Ramirez, A.P. (American Physical Society, 2006-07-01)
      We present powder and single-crystal neutron diffraction and bulk measurements of the Kagome-staircase compound Ni3V2O8 (NVO) in fields up to 8.5 T applied along the c direction. (The Kagome plane is the a-c plane.) This ...
    • From cooperative paramagnetism to Neel order in Y2Ru2O7: neutron scattering measurements 

      van Duijn, J.; Hur, N.; Taylor, J.W.; Qiu, Y.; Huang, Q.Z.; Cheong, S.-W.; Broholm, C.; Perring, T.G. (American Physical Society, 2008-01-01)
      Spin correlations in the pyrochlore antiferromagnet Y2Ru2O7 with Curie-Weiss temperature ΘCW* - 1100 K and critical temperature TN = 77 K were examined through neutron scattering. For TN < T < ΘCW / 3 the data show spin ...
    • Giant positive magnetoresistance of Bi nanowire arrays in high magnetic fields 

      Hong, Kimin; Yang, F.Y.; Liu, Kai; Reich, D.H.; Searson, P.C.; Chien, C.-L.; Balakirev, F.F.; Boebinger, G.S. (American Institute of Physics, 1999-04-15)
      We have studied the magnetoresistance of electrodeposited Bi wires with diameters between 200 nm and 2 μm in magnetic fields up to B=55 T. In zero field, the resistance increases with decreasing temperature, indicating ...
    • Inhomogeneous level splitting in Pr2-xBixRu2O7 

      van Duijn, J.; Kim, K.H.; Hur, N.; Adroja, D.; Adams, M.A.; Huang, Q.Z.; Jaime, M.; Cheong, S.-W.; Broholm, C.; Perring, T.G. (American Physical Society, 2005-05-06)
      We report that Bi doping drives Pr2-xBixRu2O7 from an antiferromagnetic insulator (x=0) to a metallic paramagnet (x≈1) with a broad low T maximum in C/T. Neutron scattering reveals local low energy spin excitations (ℎω≈1 ...
    • Ising phases of Heisenberg ladders in a magnetic field 

      Penc, K.; Fouet, J.-B.; Miyahara, S.; Tchernyshyov, O.; Mila, F. (American Physical Society, 2007-09-14)
      We show that Dzyaloshinskii-Moriya (DM) interactions can substantially modify the phase diagram of spin-1/2 Heisenberg ladders in a magnetic field provided they compete with exchange. For nonfrustrated ladders, they induce ...
    • Itinerant magnetic excitations in antiferromagnetic CaFe2As2 

      Diallo, S.O.; Antropov, V.P.; Perring, T.G.; Broholm, C.; Pulikkotil, J.J.; Ni, N.; Bud'ko, S.L.; Canfield, P.C.; Kreyssig, A.; Goldman, A.I.; McQueeney, R.J. (American Physical Society, 2009-05-08)
      Neutron scattering measurements of the magnetic excitations in single crystals of antiferromagnetic CaFe2As2 reveal steeply dispersive and well-defined spin waves up to an energy of ~100 meV. Magnetic excitations above 100 ...
    • Long-range exchange coupling between a ferromagnet and an antiferromagnet across a nonmagnetic spacer layer 

      Gokemeijer, N.J.; Ambrose, T.; Chien, C.-L.; Wang, N.; Fung, K.K. (American Institute of Physics, 1997-04-15)
      The antiferromagnet/ferromagnet exchange coupling giving rise to a shifted hysteresis loop has usually been considered an interfacial effect. We show evidence that this exchange coupling between an antiferromagnet (CoO) ...
    • Longitudinal and perpendicular exchange bias in FeMn/(FeNi/FeMn)n multilayers 

      Sun, L.; Zhou, S.M.; Searson, P.C.; Chien, C.-L. (American Institute of Physics, 2003-05-15)
      Exchange bias in ferromagnetic (FM)/antiferromagnetic (AF) bilayers is usually investigated in the longitudinal configuration with the exchange coupling established in the film plane. In this work, we report on the ...
    • Magnetic core loss of ultrahigh strength FeCo alloys 

      Cheng, X.M.; Zhang, X.K.; Zhang, D.Z.; Lee, S.H.; Duckham, A.; Weihs, T.P.; Cammarata, R.C.; Chien, C.-L. (American Institute of Physics, 2003-05-15)
      Hiperco® 50 alloy heat treated between 450 and 650°C exhibits superior mechanical properties. We report the measurements of the ac core loss at various frequencies up to 4500 Hz of the Hiperco® 50 alloy samples annealed ...
    • Magnetic dynamics of La2CuO4 studied by Mossbauer spectroscopy 

      Tang, H.; Gang, X.; Singh, A.; Tesanovic, Z.; Chien, C.-L.; Walker, J.C. (American Institute of Physics, 1990-05-01)
      By doping a very small amount of 57Fe into La2CuO4, Mossbauer spectroscopy has been applied to study the magnetic property of the parent compound. From the measurement of the magnetic hyperfine field at the Fe nuclei for ...
    • Magnetic inversion symmetry breaking and ferroelectricity in TbMnO3 

      Kenzelmann, M.; Harris, A.B.; Jonas, S.; Broholm, C.; Schefer, J.; Kim, S.B.; Zhang, C.L.; Cheong, S.-W.; Vajk, O.P.; Lynn, J.W. (American Physical Society, 2005-08-19)
      TbMnO3 is an orthorhombic insulator where incommensurate spin order for temperature TN<41 K is accompanied by ferroelectric order for T<28 K. To understand this, we establish the magnetic structure above and below the ...
    • Magnetic properties of epitaxial Mn-doped ZnO thin films 

      Cheng, X.M.; Chien, C.-L. (American Institute of Physics, 2003-05-15)
      Epitaxial ZnO thin films doped with 7% Mn have been made by reactive rf magnetron sputtering onto (112_0) sapphire substrates at 400°C. X-ray diffraction measurements reveal that the Zn0.93Mn0.07O film has a (0001) wurtzite ...
    • Magnetic properties of one-dimensional quasiperiodic Co/Pt multilayers 

      Zhu, L.Y.; Cheng, X.M.; Chien, C.-L. (American Institute of Physics, 2006-04-15)
      We have fabricated Fibonacci [Co/Pt] multilayers with two constituent Co/Pt bilayers, as well as periodic multilayers of the same Co/Pt bilayers, all of which exhibit perpendicular magnetic anisotropy. Magnetic properties ...
    • Magnetically driven ferroelectric order in Ni3V2O8 

      Lawes, G.; Harris, A.B.; Kimura, T.; Rogado, N.; Cava, R.J.; Aharony, A.; Entin-Wohlman, O.; Yildirim, T.; Kenzelmann, M.; Broholm, C.; Ramirez, A.P. (American Physical Society, 2005-08-19)
      We show that long-range ferroelectric and incommensurate magnetic order appear simultaneously in a single phase transition in Ni3V2O8. The temperature and magnetic-field dependence of the spontaneous polarization show a ...
    • Memory effects of exchange coupling in CoO/Ni81Fe19 bilayers 

      Gokemeijer, N.J.; Chien, C.-L. (American Institute of Physics, 1999-04-15)
      By changing the field-cooling procedure, the value and even the sign of the exchange field HE in CoO/Ni81Fe19 bilayers can be greatly altered. The value of HE can be made to vanish at any temperature below TN. We also show ...
    • Neutron scattering evidence for isolated spin-1/2 ladders in (C5D12N)2CuBr4 

      Nagler, S.E.; Pajerowski, D.M.; Meisel, M.W.; Broholm, C.; Schmidt, K.P.; Talham, D.R.; Brown, C.M.; Uhrig, G.S.; Savici, A.T.; Granroth, G.E. (American Physical Society, 2009-09-01)
      Inelastic neutron scattering was used to determine the spin Hamiltonian for the singlet ground-state system of fully deuterated BPCB, (C5D12N)2CuBr4. A two-leg spin-1/2 ladder model, with J⊥=(1.09±0.01) meV and J∥=(0.296±0.005) ...
    • Neutron scattering from a coordination polymer quantum paramagnet 

      Hong, T.; Kenzelmann, M.; Turnbull, M.M.; Landee, C.P.; Lewis, B.D.; Schmidt, K.P.; Uhrig, G.S.; Broholm, C.; Reich, D. (American Physical Society, 2006-09-01)
      Inelastic neutron scattering measurements are reported for a powder sample of the spin-1/2 quantum paramagnet Cu(quinoxaline)Br2. Magnetic neutron scattering is identified above an energy gap of 1.9 meV. Analysis of the ...
    • Partial order from disorder in a classical pyrochlore antiferromagnet 

      Chern, G.-W.; Moessner, R.; Tchernyshyov, O. (American Physical Society, 2008-10-01)
      We investigate theoretically the phase diagram of a classical Heisenberg antiferromagnet on the pyrochlore lattice perturbed by a weak second-neighbor interaction J2. The huge ground-state degeneracy of the nearest-neighbor ...