Is material produced for a course considered property of the department?
This is a question that really depends on local custom and policy.  At my institution, there's a clear policy that I own the copyright to materials that I produce for my teaching unless those materials were produced with extra institutional support (e.g. I'm paid extra to develop the course or the institution provides an instructional designer to help in developing a course.)
I'm aware that at many other institutions in the US, instructional content (course syllabi, lecture slides, assignments, etc.) are considered to be work for hire and owned by the institution.  This is very helpful when a course is frequently taught by contingent faculty.