Short-range ordering in a three-dimensionally frustrated magnet, Tb2Mo2O7, by wide- and small-angle neutron diffraction

Tb2Mo2O7 is an ordered crystalline oxide with the pyrochlore structure. This material undergoes a magnetic transition at 25 K which is similar to that of a spin glass. Neutron diffraction data indicate the presence of short range magnetic order via broad, diffuse reflections which persist above 25 K. Below 25 K the diffuse peaks increase in intensity but do not narrow. Fourier analysis of the data yield an approximation to the radial distribution function which is interpreted in terms of spin–spin correlations up to fourth neighbors. The first, third, and fourth neighbor interactions are ferromagnetic but the second neighbor interaction is strongly antiferromagnetic and involves only a Tb-Mo coupling. SANS data show magnetic scattering only at large Q values, reenforcing the view that antiferromagnetic interactions dominate. The Q-integrated magnetic SANS intensities show a temperature dependence similar to that for the correlation functions.