title: Two-Step Antiferromagnetic Transitions and Ferroelectricity in Spin-1 Triangular-Lattice Antiferromagnetic Sr3NiTa2O9.
abstract: We report the low-temperature characterizations on structural, specific heat, magnetic, and ferroelectric behaviors of transition metal oxide compound Sr3NiTa2O9. It is suggested that Sr3NiTa2O9 is a spin-1 triangular lattice Heisenberg quantum antiferromagnet which may have weak easy-axis anisotropy. At zero magnetic field, a two-step transition sequence at T(N1) = 3.35 K and T(N2) = 2.74 K, respectively, is observed, corresponding to the up-up-down (uud) spin ordering and 120° spin ordering, respectively. The two transition points shift gradually with increasing magnetic field toward the low temperature, accompanying an evolution from the 120° spin structure (phase) to the normal oblique phases. Ferroelectricity in the 120° phase is clearly identified. The first-principles calculations confirm the 120° phase as the ground state whose ferroelectricity originates mainly from the electronic polarization.
authors.affiliation: Laboratory of Solid State Microstructures and Innovative Center of Advanced Microstructures, Nanjing University , Nanjing 210093, China.
authors.forename: Meifeng
authors.initials: M
authors.lastname: Liu
authors.affiliation: Department of Physics, Southeast University , Nanjing 211189, China.
authors.forename: Huimin
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Physics, Southeast University , Nanjing 211189, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Huang
authors.affiliation: Laboratory of Solid State Microstructures and Innovative Center of Advanced Microstructures, Nanjing University , Nanjing 210093, China.
authors.forename: Chunyang
authors.initials: C
authors.lastname: Ma
authors.affiliation: Department of Physics, Southeast University , Nanjing 211189, China.
authors.forename: Shuai
authors.initials: S
authors.lastname: Dong
authors.affiliation: Laboratory of Solid State Microstructures and Innovative Center of Advanced Microstructures, Nanjing University , Nanjing 210093, China.|Institute for Advanced Materials and Laboratory of Quantum Engineering and Materials, South China Normal University , Guangzhou 510006, China.
authors.forename: Jun-Ming
authors.initials: JM
authors.lastname: Liu