Magnetically induced metal-insulator transition in Pb2CaOsO6

Abstract

We report on the structural, magnetic, and electronic properties of two new double-perovskites synthesized under high pressure, Pb 2 CaOsO 6 and Pb 2 ZnOsO 6 . Upon cooling below 80 K, Pb 2 CaOsO 6 simultaneously undergoes a metal-to-insulator transition and develops antiferromagnetic order. Pb 2 ZnOsO 6 , on the other hand, remains a paramagnetic metal down to 2 K. The key difference between the two compounds lies in their crystal structures. The Os atoms in Pb 2 ZnOsO 6 are arranged on an approximately face-centered cubic lattice with strong antiferromagnetic nearest-neighbor exchange couplings. The geometrical frustration inherent to this lattice prevents magnetic order from forming down to the lowest temperatures. In contrast, the unit cell of Pb 2 CaOsO 6 is heavily distorted up to at least 500 K including antiferroelectriclike displacements of the Pb and O atoms despite metallic conductivity above 80 K. This distortion relieves the magnetic frustration, facilitating magnetic order which, in turn, drives the metal-insulator transition. Our results suggest that the phase transition in Pb 2 CaOsO 6 is spin driven and could be a rare example of a Slater transition.

Metal-insulator transition and antiferromagnetism in the generalized Hubbard model: Treatment of correlation effects

“…Below in this section we consider the insulator state for which the problem acquires a pretty form. The upper subband (ν = 2) is empty and the diagonalization of the Hamiltonian (12) results in the equation of self-consistency…”

“…The first scenario corresponds to antiferromagnetic (AFM) insulating state, and the second to paramagnetic (PM) one. The Slater scenarios are realized in NaOsO 3 [7][8][9], pyrochlore oxides Ln 2 Ir 2 O 7 , Ln = Nd, Sm, Eu, Gd, Tb, Dy, and Ho [10], Cd 2 Os 2 O 7 [11], Pb 2 CaOsO 6 [12], V 2−x O 3 [13,14] and NiS 2−x Se x [15], in two latter compounds, metallic AFM phases being found. A remarkable transition from Mott to Slater electronic structure was recently observed in the AFM layer-ordered compound Sr 2 Ir 1−x Rh x O 4 [16].…”

Probing spin fluctuations in NaOsO3 by muon spin rotation and NMR spectroscopy

“…Nd 2 Ir 2 O 7 , SrIr 0.9 Sn 0.1 O 3 , CaIrO 3 and Pb 2 CaOsO 6 were recently reported to exhibit a behavior compatible with the Slater mechanism [11][12][13][14][15]. Similarly, Cd 2 Os 2 O 7 , has been at the center of the debate on the nature of MITs, as it was first predicted to be a Slater insulator [16,17], and later argued to undergo a smooth change in the electron density, with a gradual change in the Fermi surface, usually referred to as Lifshitz mechanism [18,19].…”

Magnetic Structure and Origin of Insulating Behavior in the Ba2CuOsO6 System, and the Role of A-Site Ionic Size in Its Bandgap Opening: Density Functional Theory Approaches

“…Various osmium oxide compounds exhibit attractive magnetic and electronic phenomena developed from their electron correlation effects, such as the ferromagnetic gapped state in Ba 2 NiOsO 6 [ 1 ], the singlet ground-state excitonic magnetism in Y 2 OsO 7 [ 2 , 3 , 4 ], the spin-driven metal to insulator transition in Pb 2 CaOsO 6 [ 5 ], and the unusual superconductivity in AOsO 6 (A = Cs, Rb, and K) [ 6 ].…”