Because the predominant element in steel—iron—is magnetic, most steels do have magnetic properties. This is true of many stainless steels, too. All the ferritic, martensitic, and precipitation hardening grades are magnetic.
The high nickel and chromium contents of the T300 series of austenitic stainless steels renders the alloys initially non-magnetic. For instance, a common austenitic steel, 304 stainless contains 18% chromium and 8% nickel. However, these alloys can also become magnetic during the cold-working processes used to harden them.