Magnetic anisotropy from linear defect structures in correlated electron systems

Correlated electron systems, particularly iron-based superconductors, are extremely sensitive to strain, which inevitably occurs in the crystal growth process. Built-in strain of this type has been proposed as a possible explanation for experiments where nematic order has been observed at high temperatures corresponding to the nominally tetragonal phase. Here we investigate a simple microscopic model of a strain-induced dislocation in the presence of electronic correlations, which create defect states that can drive magnetic anisotropy of this kind, if spin orbit interaction is present. Such defects can arise, e.g., in Fe-based systems or in Cu-O chains in cuprates. We estimate the contribution of these dislocations to magnetic anisotropy as detected by current torque magnetometry experiments.