Can you give us a little more information on what you mean and what material information you need?
The material files (.mtl) are just text files formatted in a certain way that Creo understands. They contain naming and mass property information relative to a material. The system comes with some preinstalled files. By default, there is no material assigned to a part file.
Those fields are optional, not mandatory. I am not aware of how the software uses them but they are not used by any of the core modeling or simulation functionality.
