Magnetic door stop
Door stoppers or holders: functions, types, installation : Magnetic Door Stop
Quote from Article entitled Door stoppers or holders: functions, types, installation:
Holders, which are attached to the top of a door leaf and a door frame, are also worth being mentioned. They will not prevent the door from being opened and closed until their being rotated at 90 degrees downward. This construction is very reliable, as it firmly holds the door in a fixed position.
The full version of the article can be found here.