a fully - pinned , flux - closed spin valve magnetoresistive sensor having a reference layer with magnetization fixed by a first antiferromagnetic layer , and a keeper layer with magnetization fixed by a second antiferromagnetic layer . the magnetization of the keeper layer is saturated and fixed in an antiparallel orientation to the pinned layer magnetization by an exchange interaction with the afm2 layer . the magnetic moments of the pinned layer and the keeper layer are approximately matched to form a flux - closed magnetic configuration wherein demagnetizing fields in the pinned layer are largely canceled and magnetostatic interaction with the free layer is reduced . saturation of the keeper layer magnetization by exchange coupling with the afm 2 layer eliminates or reduces magnetization canting at the edges of the keeper layer which can result in signal field shunting through the keeper layer . afm 1 and afm 2 layers may be formed of the same antiferromagnetic material , such as nio , or alternatively may be formed of different antiferromagnetic materials , such as ni — mn and nio , respectively .