  Artificial spin ices are engineered arrays of dipolarly coupled nanobar
magnets. They enable direct investigations of fascinating collective phenomena
from their diverse microstates. However, experimental access to ground states
in the geometrically frustrated systems has proven difficult, limiting studies
and applications of novel properties and functionalities from the low energy
states. Here, we introduce a convenient approach to control the competing
diploar interactions between the neighboring nanomagnets, allowing us to tailor
the vertex degeneracy of the ground states. We achieve this by tuning the
length of selected nanobar magnets in the spin ice lattice. We demonstrate the
effectiveness of our method by realizing multiple low energy microstates in a
Kagome artificial spin ice, particularly the hardly accessible long range
ordered ground state - the spin crystal state. Our strategy can be directly
applied to other artificial spin systems to achieve exotic phases and explore
new emergent collective behaviors.
