Figure 1

Inverse magnetic susceptibility of $\mathrm{Y}\mathrm{Ba}{\mathrm{Co}}_4{\mathrm{O}}_7$ collected at $1000\mathrm{Oe}$. The dotted line is a fit of the high-temperature data with a Curie-Weiss law.Reuse & Permissions

Figure 2

(Color online) (a) Thermodiffractogram of $\mathrm{Y}\mathrm{Ba}{\mathrm{Co}}_4{\mathrm{O}}_7$ collected on GEM. Data from a bank of detectors situated at $34.96°2\Theta$ are shown. The scattering intensity is color coded and shown on a logarithmic red (gray) scale. (b) Rietveld refinement at $2\mathrm{K}$. The gray crosses and dashed solid line represent the experimental data points and calculated diffraction pattern, respectively. The difference is shown at the bottom as a solid line. The row of markers shows the positions of the nuclear and magnetic reflections. The thick solid line represents the contribution from magnetic scattering alone. The inset of (b) displays a section of the neutron diffraction pattern collected at $115\mathrm{K}$ on GEM showing the coexistence of nuclear Bragg scattering and magnetic diffuse scattering. The solid line is a fit to the data. The diffuse magnetic scattering is modeled by a Lorentzian profile function.Reuse & Permissions

Figure 3

(Color online) Top: Magnetic structure of $\mathrm{Y}\mathrm{Ba}{\mathrm{Co}}_4{\mathrm{O}}_7$ projected in the $ab$ plane at 2 (top panel) and $80\mathrm{K}$ (bottom). The black and gray arrows represent moments on the Co(1) and Co(2) sites, respectively (see text for details). For clarity only one of the two $\mathrm{Co}\left(1\right)∕\mathrm{Co}\left(2\right)$ layers is shown, i.e., atoms with fractional coordinates $z>0.5$. Magnetic moments on the second layer, not shown, are related by time reversal of the $2_1$ symmetry operator. Bottom: Exchange interactions $J_1$ and $J_2$ are depicted as black (thin) and blue (thick) lines respectively. The ideal 120° structure is also shown (see text for details).Reuse & Permissions

Figure 4

(a) Temperature dependence of the magnetic moment on the Co(1) and Co(2)–Co(4) sites. (b) Integrated intensities of selected magnetic peaks (labels) versus temperature. (c),(d) Angular deviations from the ideal 120° model for Co ions labeled 1–4 (see Fig. 3 and text for details).Reuse & Permissions