= Solution
\b[Weak <ferromagnetism> from canted antiferromagnetic order is the consistent model.] Importantly, the plot has different <magnetization> scales: the left axis belongs to Mn and Fe; the right belongs to Co and Ni. Approximate low-temperature field-cooled readings are 40, 50, 450 and 390 G cm$^3$ mol$^{-1}$, respectively. Dividing by 5585 gives
$$
\boxed{M_{\rm FC}\simeq(0.0072,\ 0.0090,\ 0.081,\ 0.070)\ \mu_B\text{ per metal}.}
$$
These moments are tiny compared with fully aligned moments of about 5.09, 4.40, 4.25 and 2.47 $\mu_B$, calculated using the Curie-derived $g$ values below. A conventional ferromagnet of the full high-spin ions would have much larger spontaneous <magnetization>; a simple bipartite array of identical metal sites also supplies no obvious unequal sublattice moments for ferrimagnetism. Opposed large sublattice moments with a small transverse uncompensated component reconcile the net response with negative $\Theta$.
If the 10 Oe field has aligned the weak-ferromagnetic domains, $M_{\rm weak}=gS\mu_B\sin\alpha$ estimates sublattice canting angles of roughly 0.08°, 0.12°, 1.1° and 1.6°. These are illustrative, not precision structure determinations: the low field may not fully align the domains, and the readings are graphical. Bulk <magnetization> strongly supports this model but does not uniquely establish every <spin> direction; <magnetic neutron diffraction> would test the microscopic arrangement.
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