Oxygen miscibility gap and spin glass formation in the pyrochlore Lu2Mo2O7

• Published in: Journal of solid state chemistry 2013-07, Vol.203, p.199-203
• Main Authors: Clark, L., Ritter, C., Harrison, A., Attfield, J.P.
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Frustrated magnets; Glass transitions; Neutron diffraction and scattering; Phase separation; Physics; Pyrochlore oxides; Single-crystal and powder diffraction; Solubility, segregation, and mixing; phase separation; Specific phase transitions; Structure of solids and liquids; crystallography
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2013.04.012

Rare earth (R) molybdate pyrochlores, R2Mo2O7, are of interest as frustrated magnets. Polycrystalline samples of Lu2Mo2O7−x prepared at 1600°C display a coexistence of cubic pyrochlore phases. Rietveld fits to powder neutron diffraction data and chemical analyses show that the miscibility gap is between a stoichiometric x=0 and an oxygen-deficient x≈0.4 phase. Lu2Mo2O7 behaves as a spin glass material, with a divergence of field cooled and zero field cooled DC magnetic susceptibilities at a spin freezing temperature Tf=16K, that varies with frequency in AC measurements following a Vogel–Fulcher law. Lu2Mo2O6.6 is more highly frustrated spin glass and has Tf=20K. The cubic Lu2Mo2O7−x system exhibits a miscibility gap between coexisting pyrochlore phases at 1600°C. Neutron powder diffraction refinement and chemical analysis shows that the gap separates stoichiometric x=0 and oxygen-deficient x≈0.4 phases. Lu2Mo2O7−x has a frustrated spin glass ground state that is sensitive to the oxygen content. [Display omitted] •The cubic Lu2Mo2O7−x system has a miscibility gap between coexisting pyrochlore phases at 1600°C.•Neutron powder diffraction shows that the gap separates x=0 and oxygen-deficient x≈0.4 phases.•Lu2Mo2O7−x has a frustrated spin glass ground state that is sensitive to the oxygen content.