Hohenberg—Mermin—Wagner theorem

In accord with the Hohenberg-Mermin-Wagner theorem [15] the considered two-dimensional system is in the paramagnetic state for T > 0. This result can also be obtained using Eq. (8). Also it can be shown [7] that in the infinite crystal at T = 0 the long-range antiferromagnetic order is destroyed for the hole concentrations x > xc 0.02. 

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