Fig. 3.

Elastic magnetic scattering from BaCo₂(AsO₄)₂ at T = 1.7 K as a function of field applied perpendicular to the scattering plane and along the $(\overline{1}20)$ direction. The scattering has been averaged in the energy transfer window of ±0.1 meV and k ∈ [ − 0.1, 0.1] along the (0k0) direction. The short-ranged nature of the correlations is evident at zero field (A) and in the commensurate ordered state at μ ₀ H = 0.4 T (B) through the broadness of the peaks in the (00l) direction. Panels (E and F) further highlight this, comparing cuts at the respective incommensurate wavevectors q(H)≡{q _h (H),0, q _l (H)}. For μ ₀ H = 0 T, q = (0.27, 0, −1.31) and for μ ₀ H = 0.4 T q = (1/3, 0, −1.31). Panel (G) compares cuts along the (h00) direction over the (003) structural Bragg peak. The increase in intensity in the field-polarized 3 T phase may be directly accounted for by the induced in-plane moment. The full width of the averaging windows for cuts in (E) and (G) are Δ k = 0.1 and Δ l = 0.6 and for (F) from Δ h = Δ k = 0.1. (H–K) Constant energy slices around the Γ point gap energy at four representative fields. The energy windows for panels (H–J) begin at ℏω = 0.4 meV and extend to ℏω = 1.58 meV, 1.80 meV, 1.90 meV, and 2.29 meV, respectively. Dashed white lines are shown at the incommensurate ordering wavevector for each respective field, with no lines for the magnetized phases without AFM order.