  We observe strong dynamical suppression of optically induced loss in a weakly
interacting Fermi gas as the $s$-wave scattering length is increased. The
single, cigar-shaped cloud behaves as a large spin lattice in energy space with
a tunable Heisenberg Hamiltonian. The loss suppression occurs as the lattice
transitions into a magnetized state, where the fermionic nature of the atoms
inhibits interactions. The data are quantitatively explained by incorporating
spin-dependent loss into a quasi-classical collective spin vector model, the
success of which enables the application of optical control of effective
long-range interactions to this system.
