La2CoO4.25 was shown to order antiferromagnetically at 36 K with both oxygen and charge ordering via neutron diffraction . In contrast, La2CoO4 undergoes a Néel-type order at 275 K and a structural transition at 135 K to the tetragonal phase . For the substituted La2Ni0.75Co0.25O4.08 composite, no sharp transitions in susceptibility were expected due to the observations on the two parent compounds. As shown the red curve in Figure , the susceptibility versus temperature in an applied field of 1 T shows a broad maximum in the susceptibility around 200 K, with the onset of an increase around 250 K. As the composite La2Ni0.75Co0.25O4.08 (black curve) already has an extended oxygen content no clear magnetic transition is expected and the origin of this maximum originates from the exchange interaction in low dimensional quantum magnets as this typical 2D Heisenberg magnet. The base sample for the reaction is a mixture of the La2Ni0.75Co0.25O4.08 composite with La0.9Ba0.1F2.9, which shows in the entire temperature range a paramagnetic contribution due to the nonmagnetic sample signal mixed with the sample holder (see Figure ). The charged samples also contain diamagnetic graphene nanoparticles leading to largely changed signal shown in Figure a, where no maximum is apparent. Thus, for the measurements it was tried to extract solely the La2Ni0.75Co0.25O4.08Fy part from the pellet. Hence, we plot the effective susceptibility in emu/Oe g -1 and note that the precise mass ratios of each sample might vary slightly, due to the different amounts of contamination with the base mixture as described earlier by Vasala et al. 53 For the M(H) curves, a subtle hysteresis dominated by a Brillouin function with a very low moment of 0.002 µB for the pure La2Ni0.75Co0.25O4.08 was observed (not shown). Given the impossibility of dividing by the real molar masses due to a mixture in the fluorinated compounds, the M(H) curves in detail was not analysed but found in all a similar shape and coercivity.