  Exclusive production of $\phi$ mesons on hydrogen and deuterium targets is
studied in the HERMES kinematic region $1 < Q^{2} < 7$ GeV$^2$ and $3.0 < W <
6.3$ GeV. Spin density matrix elements and their $Q^{2}$ and $t$ dependences
are presented. These data are consistent with s-channel helicity conservation
in exclusive $\phi$ meson production. No significant evidence for the
contribution of unnatural-parity-exchange amplitudes is found.
