Antiferromagnetic Mott insulating state in single crystals of the hexagonal lattice material Na2IrO3
By Y. Singh, Philipp Gegenwart. 2010
279 citations recorded by the source corpus.
We have synthesized single crystals of Na_2IrO_3 and studied their structure, transport, magnetic, and thermal properties using powder x-ray diffraction (PXRD), electrical resistivity, isothermal magnetization M versus magnetic field H, magnetic susceptibility \chi versus temperature T, and heat capacity C versus T measurements. Na_2IrO_3 crystallizes in the monoclinic \emph{C2/c} (No. 15) type structure which is made up of Na and NaIr_2O_6 layers alternately stacked along the c axis. The \chi(T) data show Curie-Weiss behavior at high T > 200K with an effective moment \mu_eff = 1.82(1) \mu_B indicating an effective spin S_eff = 1/2 on the Ir^4+ moments. A large Weiss temperature \theta = - 116(3)K indicates substantial antiferromagnetic interactions between these S_eff = 1/2, Ir^4+ moments. Sharp anomalies in \chi(T) and C(T) data indicate that Na_2IrO_3 undergoes a transition into a long-range antiferromagnetically ordered state below T_N = 15 K. The magnetic entropy at T_N is only about 20% of what is expected for S_eff = 1/2 moment ordering. The reduced entropy and the small ratio T_N/\theta \approx 0.13 suggest geometrical magnetic frustration and/or low-dimensional magnetic interactions in Na_2IrO_3. In plane resistivity measurements show insulating behavior. This together with the local moment magnetism indicates that bulk Na_2IrO_3 is a Mott insulator.
Subfields: Atomic and Molecular Physics, and Optics, Condensed Matter Physics
View Paper: https://www.semanticscholar.org/paper/2f6400a751d4ae410b52e62c2dfd882b14b649f4
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Citations in the corpus
- Kitaev materials (2017, methodology): “1 Na2IrO3 Na2IrO3 was independently synthesized to explore its potential for Kitaev physics in 2009/2010 by the groups of Takagi [78] and Gegenwart [79].”