I would say, 「心が安らぐ」　would be "to feel at peace" because 「心」 means "mind" in this context. You could say "Mind is relaxed" but if you use it in a sentence like this:　 「この音楽を聴くと、心が安らぐ」 It would be "Listening to this music makes me feel at peace"

Yes.it is good.