A divine focus component is an item of spiritual significance. The divine focus for a cleric or a paladin is a holy symbol appropriate to the character’s faith. The divine focus for a druid or a ranger is a sprig of holly, or some other sacred plant.
If the Components line includes F/DF or M/DF, the arcane version of the spell has a focus component or a material component (the abbreviation before the slash) and the divine version has a divine focus component (the abbreviation after the slash).
However, rather than having a Components entry of F/DF or M/DF, some spells have only a DF entry. For example, the 1st-level Sor/Wiz spells magic weapon and stone shield have DF entries rather than F/DF or M/DF entries.
Besides extrapolating from or assuming based on the text quoted above, do the rules elsewhere actually say whether or not an arcane caster can (or must) satisfy this standalone DF-only component?
Note: A similar question is asked here.