A magnetoresistive (MR) sensor including a synthetic antiferromagnetic (SAF) structure that is magnetically coupled to a side shield element. The SAF structure includes at least one magnetic amorphous layer that is an alloy of a ferromagnetic material and a refractory material. The amorphous magnetic layer may be in contact with a non-magnetic layer and antiferromagnetically coupled to a layer in contact with an opposite surface of the non-magnetic layer.