Can the freezing point of Nitrogen be reduced?

Low temperature phase diagrams are reasonably abundant in the literature. For simplicity I considered an oxygen-nitrogen mixture which, at the right proportions, is basically air.

C.S. Barrett et al. in the Journal of Chemical Physics published just such a paper in 1967. Figure 1 shows the phase diagram they determined. Adding oxygen to nitrogen lowers the freezing point, with a eutectic at about 50K at perhaps 22 at.% nitrogen. However, the ~20 at.% oxygen in air looks to drop the freezing point of nitrogen by some 7K or so.