Electric field induced reversible 180° magnetization switching through tuning of interfacial exchange bias along magnetic easy-axis in multiferroic laminates

E-field control of interfacial exchange coupling and deterministic switching of magnetization have been demonstrated in two sets of ferromagnetic(FM)/antiferromagnetic(AFM)/ferroelectric(FE) multiferroic heterostructures, including NiFe/NiCoO/glass/PZN-PT (011) and NiFe/FeMn/glass/PZN-PT (011). We designed this experiment to achieve exchange bias tuning along the magnetic easy axis, which is critical for realizing reversible 180 degrees magnetization deterministic switching at zero or small magnetic bias. Strong exchange coupling were established across AFM-FM interfaces, which plays an important role in voltage control of magnetization switching. Through the competition between the E-field induced uniaxial anisotropy in ferromagnetic layer and unidirectional anisotropy in antiferromagnetic layer, the exchange bias was significantly shifted by up to vertical bar Delta H-ex vertical bar/H-ex = 8% in NiFe/FeMn/glass/PZN-PT (011) and 13% in NiFe/NiCoO/glass/PZN-PT (011). In addition, the square shape of the hysteresis loop, as well as a strong shape tunability of vertical bar Delta H-ex vertical bar/H-c = 67.5 similar to 125% in NiFe/FeMn/glass/PZN-PT and 30 similar to 38% in NiFe/NiCoO/glass/PZN-PT were achieved, which lead to a near 180 degrees magnetization switching. Electrical tuning of interfacial exchange coupling in FM/AFM/FE systems paves a new way for realizing magnetoelectric random access memories and other memory technologies.