High temperature linear magnetoresistance and scaling behavior in the Ba(Fe${_{1-x}}$Co${_{x}}$)$_{2}$As$_{2}$ series

Abstract

We present magnetotransport studies of the parent, an underdoped and an optimally doped composition of the Ba(Fe${_{1-x}}$Co${_{x}}$)${_{2}}$As${_{2}}$ series. We observe that both the Kohler's and modified Kohler's scaling is typically violated in both the magnetically ordered and paramagnetic regimes. A notable exception is the magnetically ordered state of the underdoped composition where the modified Kohler's scaling is observed, indicating its relative similarity to the cuprates and some heavy fermion systems. This composition also exhibits a feature in the Hall angle, which could signify the opening of a pseudogap before the onset of long range magnetic order. Interestingly, the transverse magnetoresistance is seen to exhibit a linear field dependence in the paramagnetic regimes of all these compositions. We also demonstrate that the $B/T$ scaling proposed recently in the context of quantum critical systems is seen to be valid in all these systems. The implications of our observations are discussed in the context of magnetotransport of metals with incipient magnetic fluctuations.