Abstract
The authors describe a broken C4 lattice symmetry in the tetragonal phase of BaCo${}_{0.9}$Ni${}_{0.1}$S${}_{1.9}$.
Highlights
Broken symmetries are sometimes hindered in a highsymmetry state due to degeneracy
When the tetragonal state is weakly distorted to an orthorhombic state by a uniaxial pressure, the lattice distortion leads to a manifestation of one magnetic domain [11,12,13]
We report that the Q2 domain out of coexisting Q1 and Q2 domains becomes dominant by applying a weak in-plane uniaxial pressure of 1 MPa in the AF insulator (AFI) phase of BCNS
Summary
Broken symmetries are sometimes hindered in a highsymmetry state due to degeneracy. Such a state inevitably accompanies with strong fluctuations, leading to intrinsic novel properties different from the others. When the tetragonal state is weakly distorted to an orthorhombic state by a uniaxial pressure, the lattice distortion leads to a manifestation of one magnetic domain [11,12,13] Such a domain change is observed in BaFe2As2 under a uniaxial pressure of ∼0.7 MPa along the b-axis [10]. Our inelastic neutron scattering (INS) measurements of the crystal at a weak uniaxial pressure of 1 MPa reveals a characteristic in-plane anisotropy of magnetic excitation in the tetragonal state. The spectra of BCNS in the insulator phase are described by a spin-wave model with Q1 and Q2 domains, leading to the estimation of the exchange couplings It provides us quantitative information on the magnetic excitation stabilizing the novel stripe order in the tetragonal state.
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