Unlike groups, libraries owned by individual users cannot be shared to a department. Department libraries can only be created by the system admin or department admin. This is for the purpose for more consolidated control of the libraries.
For system admin to create a shared library in the (sub)department:
1. Go to the system admin interface: click the person icon at the top right corner and click Organization Admin.
2. Click Departments on the left panel.
3. Select the department(then select the sub-department) you would like to create the library.
4. Click New Library.
5. Enter the library name and click Submit.