Antiferromagnetic and Ferro-Orbital Correlations (From a book )

Unlike the checkerboard (G-type) antiferromagnetism in cuprates [2] that is dictated by strong first-neighbor antiferromagnetic coupling, the parent compounds of iron pnictides mostly host a ( ,0)-collinear (C-type) antiferromagnetic order: antiferromagnetic in the x-direction but ferromagnetic along the other y-direction [3, 16]. DFT has been successful in predicting the magnetic structure for various iron-based superconductors, even for the bicollinear antiferromagnetic FeTe [52]. Here, we focus on the more common C-type antiferromagnetic order. Within the local Heisenberg picture, this stripe-like structure can be created by requiring the next-nearest-neighbor coupling, J2, to be larger than half of the nearest-neighbor antiferromagnetic coupling, J1 [12–14]. The competition between C-type and G-type antiferromagnetism implies a strong magnetic frustration [12–14]. This frustration should be at least partially responsible for the observed small spin moment and for promoting superconductivity [12]. This magnetic frustration also find analogy to the physics of the cuprates [13].

Reference:  The book     Iron-Based Superconductivity

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