Structure and magnetic properties of the pyrochlore Sc2Mn2O7

Sc2Mn2O7 has been prepared at 60 kbar and the crystal structure has been determined from Rietveld analysis of x-ray powder diffraction data. A cubic pyrochlore structure is found described in space group Fd3m with a=9.5965(4) Å. Magnetic susceptibility data conform to the Curie-Weiss law in the range 175 K to 300 K with an effective moment of 3.6(1) μBMn and θp = +77(3) K indicating the predominance of ferromagnetic interactions. Nonetheless, the material does not show long range magnetic order and instead a spin glass like transition is found below 17 K. Thus, Sc2Mn2O7 resembles Y2Mn2O7 and Lu2Mn2O7, both spin glass materials, rather than In2Mn2O7 and Tl2Mn2O7 which are ferromagnetic below 120 K. The compound is red-orange in color and is an insulator in contrast to the other manganate pyrochlores which are semiconductors.