(color online) (a) Normalized Kerr rotation hysteresis curves along the -direction under different E-fields. The inset shows the in-plane strain difference (ε_y − ε_x) as a function of the E-fields (from Fig.3 in Ref. [50]). (b) Angular dependence of M_r/M_s with E = 0 (open square), 4 kV/cm (open circle), and after releasing 4 kV/cm (open triangle) E-fields. The inset gives the M–H loops without the E-field and after releasing 4 kV/cm E-fields (from Fig. 2 in Ref. [52]). (c) Voltage-impulse-induced non-volatile switching of FMR frequency in FeCoB/(011) PMN-PT heterostructures (from Fig. 1(f) in Ref. [53]). (d) Schematics of the E-field-induced ferroelectric/ferroelastic domain switching pathways in (011) oriented PZN-PT single crystal substrates (from Fig. S1(b) in Ref. [49]).