In general, steels are magnetic. However, the addition of certain elements in a select group of steels, such as the addition of nickel into the alloy, changes the physical properties of steel. This modification results in steel no longer having magnetism.
Steels are classified by several names, some have magnetism and some do not. Steel in its basic form is ferritic and magnetic. The addition of chromium and carbon makes steel harder and places it into a category of martensitic. These steels are still magnetic. Higher amounts of chromium and the addition of nickel place steels in the category of austenitic. The nickel in these steels renders them non-magnetic.