  Antiferromagnets (AFMs) with zero net magnetization are proposed as active
elements in future spintronic devices. Depending on the critical thickness of
the AFM thin films and the measurement temperature, bimetallic Mn-based alloys
and transition metal oxide-based AFMs can host various coexisting ordered,
disordered, and frustrated AFM phases. Such coexisting phases in the exchange
coupled ferromagnetic (FM)/AFM-based heterostructures can result in unusual
magnetic and magnetotransport phenomena. Here, we integrate chemically
disordered AFM IrMn3 thin films with coexisting AFM phases into complex
exchange coupled MgO(001)/Ni3Fe/IrMn3/Ni3Fe/CoO heterostructures and study the
structural, magnetic, and magnetotransport properties in various magnetic field
cooling states. In particular, we unveil the impact of rotating the relative
orientation of the disordered and reversible AFM moments with respect to the
irreversible AFM moments on the magnetic and magnetoresistance properties of
the exchange coupled heterostructures. We further found that the persistence of
AFM grains with thermally disordered and reversible AFM order is crucial for
achieving highly tunable magnetic properties and multi-level magnetoresistance
states. We anticipate that the introduced approach and the heterostructure
architecture can be utilized in future spintronic devices to manipulate the
thermally disordered and reversible AFM order at the nanoscale.
