Intrinsic pinning by naturally occurring correlated defects in FeSe1-xTex superconductors.

We study the angular dependence of dissipation in the superconducting state of FeSe and Fe(Sei(1-x)Te(x)) through electrical transport measurements, using crystalline intergrown materials. We reveal the key role of the inclusions of the non superconducting magnetic phase Fe1-y(Se1-xTex), growing into the Fe(Se1-xTex) pure beta-phase, in the development of a correlated defect structure. The matching of both atomic structures defines the growth habit of the crystalline material as well as the correlated planar defects orientation.