Abstract
We use neutron scattering to study the effect of uniaxial pressure on the tetragonal-toorthorhombic
structural (Ts) and paramagnetic-to-antiferromagnetic (TN) phase transitions in
NaFeAs and compare the outcome with similar measurements on as-grown and annealed BaFe2As2.
In previous work on as-grown BaFe2As2, uniaxial pressure necessary to detwin the sample was found
to induce a significant increase in zero pressure TN and Ts. However, we find that similar uniaxial
pressure used to detwin NaFeAs and annealed BaFe2As2 has a very small effect on their TN and Ts.
Since transport measurements on these samples still reveal resistivity anisotropy above TN and Ts,
we conclude that such anisotropy cannot be due to uniaxial strain induced TN and Ts shifts, but
must arise from intrinsic electronic anisotropy in these materials.
