2010/03/04 by Yogesh Singh, Singh, Yogesh, P. Gegenwart +1
Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #FOS: Physical sciences #Glass properties and applications #Materials Science (cond-mat.mtrl-sci) #Strongly Correlated Electrons (cond-mat.str-el) #Theoretical and Computational Physics
paper · pdf · doi:10.48550/arxiv.1003.0973
openalex publication_date 2010/03/04 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We have synthesized the novel material Na2IrO3 and studied its structure, transport, magnetic, and thermal properties using powder x-ray diffraction (PXRD), electrical resistivity, isothermal magnetization M versus magnetic field H, static χand dynamic χac magnetic susceptibility versus temperature T, and heat capacity C versus T measurements. Na2IrO3 crystallizes in the monoclinic C2/c (No. 15) structure which is made up of Na and NaIr2O6 layers alternately stacked along the c axis. From a Rietveld refinement of the PXRD pattern we identify atomic disorder arising from a mixing of Ir and Na sites within the NaIr2O6 layers. The χdata in H = 1 T shows Curie-Weiss behavior at high T > 100 K with an effective moment μeff = 1.82(1) μB indicating an effective spin Seff = 1/2 on the Ir4+ moments. A Weiss temperature θ= - 62(1) K indicates substantial antiferromagnetic interactions between these Seff = 1/2, Ir4+ moments. The χdata in low field show a sharp cusp at Tg = 5.5 K and there is a bifurcation between zero-field-cooled (ZFC) and field-cooled (FC) data below this T. The χac data also show a sharp cusp at Tg = 5.5 K at a frequency f = 1 Hz which moves to higher temperatures with increasing f. We did not observe any anomaly at Tg in our C measurements and only a broad shoulder was observed at a much higher T = 12 K. Our results indicate that in Na2IrO3, a spin-glass like state occurs below the freezing temperature Tg = 5.5 K and this freezing most likely arises either from structural disorder or geometrical magnetic frustration.