Neutron-diffraction study of magnetic ordering in the pyrochlore series R2Mo2O7 (R=Nd,Tb,Y)

Abstract

${\mathrm{Nd}}_2$ ${\mathrm{Mo}}_2$ ${\mathrm{O}}_7$, ${\mathrm{Y}}_2$ ${\mathrm{Mo}}_2$ ${\mathrm{O}}_7$, and ${\mathrm{Tb}}_2$ ${\mathrm{Mo}}_2$ ${\mathrm{O}}_7$ are all ordered crystalline oxides with the cubic pyrochlore structure. At 53 K, ${\mathrm{Nd}}_2$ ${\mathrm{Mo}}_2$ ${\mathrm{O}}_7$ is long-range ordered with a ferrimagnetic structure. A transition temperature of 95 K is determined from small-angle-neutron-scattering (SANS) data. Antiferromagnetic structures are proposed below 20 K that are consistent with previous magnetization results. No magnetic scattering from ${\mathrm{Y}}_2$ ${\mathrm{Mo}}_2$ ${\mathrm{O}}_7$ was observed at low temperature, which is believed to be a result of the small moment on ${\mathrm{Mo}}^{4+}$. For ${\mathrm{Tb}}_2$ ${\mathrm{Mo}}_2$ ${\mathrm{O}}_7$ strong diffuse scattering from the large ${\mathrm{Tb}}^{3+}$ moments is observed below 25 K. Fourier analysis of this data yields an approximation to the radial correlation function, which gives information concerning spin-spin correlations for the first four coordination shells. The first-, third-, and fourth-neighbor correlations are ferromagnetic, but the second-neighbor correlation is strongly antiferromagnetic. SANS data show magnetic scattering only at large Q, reenforcing the view that antiferromagnetic interactions dominate. The Q-integrated magnetic SANS shows a temperature dependence similar to that for the correlation functions. The long-range order in ${\mathrm{Nd}}_2$ ${\mathrm{Mo}}_2$ ${\mathrm{O}}_7$ and lack of long-range order in ${\mathrm{Y}}_2$ ${\mathrm{Mo}}_2$ ${\mathrm{O}}_7$ and ${\mathrm{Tb}}_2$ ${\mathrm{Mo}}_2$

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This publication has 21 references indexed in Scilit:

• Magnetic and electrical properties of R2Mo2O7 pyrochlore compounds
  Journal of Solid State Chemistry, 1989
• The crystal structure of the spin-glass pyrochlore, Y2Mo2O7
  Journal of Solid State Chemistry, 1988
• Ferromagnetic R2Mn2O7 pyrochlores (R = DyLu, Y)
  Journal of Solid State Chemistry, 1988
• Electrical resistivity of pyrochlore compounds R2Mo2O7(R =Nd, Sm, Gd, Tb, Y)
  Journal of Solid State Chemistry, 1987
• Pyrochlore solid solutions (LaxY1−x)2Mo2O7, x = 0.0 to 0.5. Spin-glass-like behavior
  Journal of Solid State Chemistry, 1987
• Spin-glass-like behavior in Y2Mo2O7, a concentrated, crystalline system with negligible apparent disorder
  Solid State Communications, 1986
• Magnetic properties and magnetic ordering in the Rare Earth Molybdenum(IV) Pyrochlores: R₂Mo₂O₇
  Zeitschrift für anorganische und allgemeine Chemie, 1986
• Magnetic properties of RE2Mo2O7 pyrochlores
  Journal of Low Temperature Physics, 1983
• Oxide pyrochlores — A review
  Progress in Solid State Chemistry, 1983
• Electrical properties of Ln2Mo2O7 pyrochlores (Ln=SmYb,Y)
  Materials Research Bulletin, 1980

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