  In artificial spin ice systems, an interplay of defects and dipolar
interactions is expected to play important roles in stabilizing different
collective magnetic states. In this work, we investigated the magnetization
reversal of individual defective square artificial spin ice vertices where
defects break four-fold rotational symmetry of the system. By varying the angle
between the applied field and the geometrical axis of the vertices, we observe
a change in energy landscape of the system resulting into the stabilization of
collective low-energy magnetic states. We also observe that by changing the
angle, it is possible to access different vertex configurations. Micromagnetic
simulations are performed for varying angle as well as external field, the
results of which are consistent with the experimental data.
