Angular and field properties of the critical current and melting line of Co-doped SrFe2As2 epitaxial films

We present measurements of the field and angular dependence of the critical current density (J(c)) and melting line made using transport and magnetization techniques for SrFe1.8Co0.2As2 (nominal composition) biaxially oriented films. At high magnetic fields the angular dependence of the melting line and J(c) (for mu H-0 > 2 T) can be successfully scaled using an anisotropic scaling with gamma = 2, indicating a random-point-like pinning contribution. At lower fields, angular and field J(c) dependences strongly depend on the magnetic field history. We find a hysteretic behaviour of J(c) with H with higher J(c) in the descending branch, similar to that attributed to magnetic pinning and granularity effects. Furthermore this allows us to tune J(c)(Theta) such that a J(c) peak along the c axis can be enhanced up to 30%. The low values of J(c) measured suggest that granularity depresses J(c) but does not rule out the possibility of dilute magnetic pinning.