  We report time-of-flight inelastic neutron scattering (INS) investigations on
the spin fluctuation spectrum in the 112-type iron-based superconductor (FeSC)
Ca$_{0.82}$La$_{0.18}$Fe$_{0.96}$Ni$_{0.04}$As$_{2}$ (CaLa-112). In comparison
to the 122-type FeSCs with a centrosymmetric tetragonal lattice structure
(space group $I4/mmm$) at room temperature and an in-plane stripe-type
antiferromagnetic (AF) order at low temperature, the 112 system has a
noncentrosymmetric structure (space group $P2_{1}$) with additional zigzag
arsenic chains between Ca/La layers and a magnetic ground state with similar
wavevector $\mathbf{Q}_{\mathrm{AF}}$ 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 $\langle m^2 \rangle\approx 4.6\pm0.2 \mu_B^2$/Fe are
larger than 122 system, the dynamic correlation lengths are similar
($\xi\approx 10$ \AA). 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.
