Are there Atmel and PIC libraries for Eagle?
The answer to your question is really not the answer you want to hear.

You could use a search engine to search for user generated EAGLE CAD files for Atmel chips but you may receive files that are poorly designed or old. Unless the files are from a co-worker or a capable individual that I know: I wouldn't trust other files.

It's usually always best to generate your own library so you ensure your parts comply with the device's datasheet. Creating your own parts for EAGLE is a good skill to learn, albeit a tedious one at times.

I found this 2 part video series by Hackaday very helpful when I started getting into EAGLE:

https://www.youtube.com/watch?v=irE4oHB5fSc

There's so many other guides easily searchable online.