We use magnetic force microscopy (MFM) to characterize superconductivity across the superconducting dome in BaFe₂(As_1-xP_x)₂, a pnictide that exhibits a peak in the penetration depth (λ_ab) at optimal doping (x_opt), as previously shown in sample wide measurements [1]. Our local measurements show a peak at x_opt and a T_C vs. λ_ab^-2 dependence that is similar on both sides of x_opt. Near the underdoped edge of the superconducting dome λ_ab increases sharply suggesting that superconductivity competes with another phase. Indeed MFM vortex imaging shows correlated defects parallel to twin boundaries only in underdoped samples and not for x≥x_opt. Furthermore magnetic scans in these samples reveal stripes parallel to twin boundaries even in the absence of magnetic field.

[1] K. Hashimoto et al., Science 336, 1554 (2012).