Spin fluctuations in the 112-type iron-based superconductor CaLaFeNiAs

Xie, T.*; Liu, C.*; Kajimoto, Ryoichi  ; Ikeuchi, Kazuhiko*; Li, S.*; Luo, H.*

We report time-of-flight inelastic neutron scattering (INS) investigations on the spin fluctuation spectrum in the 112-type iron-based superconductor (FeSC) CaLaFeNiAs (CaLa-112). In comparison to the 122-type FeSCs with a centrosymmetric tetragonal lattice structure (space group ) at room temperature and an in-plane stripe-type antiferromagnetic (AF) order at low temperature, the 112 system has a noncentrosymmetric structure (space group ) with additional zigzag arsenic chains between Ca/La layers and a magnetic ground state with similar wavevector but different orientations of ordered moments in the parent compounds. Our INS study clearly reveals that the in-plane dispersions and the bandwidth of spin excitations in the superconducting CaLa-112 closely resemble to those in 122 systems. While the total fluctuating moments /Fe are larger than 122 system, the dynamic correlation lengths are similar ( ). These results suggest that superconductivity in iron arsenides may have a common magnetic origin under similar magnetic exchange couplings with a dual nature from local moments and itinerant electrons, despite their different magnetic patterns and lattice symmetries.