Apparatus and associated methods relate to a magnetoresistive sensor element with synthetic antiferromagnetic biasing structure separated, by a non-magnetic tuning spacer, from a free ferromagnetic layer of a TMR/GMR sensor. The synthetic antiferromagnetic biasing structure includes first and second ferromagnetic layers separated from one another by a synthetic antiferromagnetic spacer. The synthetic antiferromagnetic biasing structure is biased during manufacture and pinned via exchange coupling with an adjacent antiferromagnetic layer. The synthetic antiferromagnetic biasing structure biases the free ferromagnetic layer via tuned exchanged coupling via relative proximity controlled by thickness of the non-magnetic tuning spacer.