Significant enhancement of magnetoelectric effect in Metglas-langatate-Metglas monolithic structure through annealing

This paper investigates the influence of annealing in a magnetic field on the magnetoelectric (ME) properties of monolithic Metglas-langatate-Metglas heterostructure. The composite structure comprises amorphous magnetic Metglas layers (Fe77Co4.3Si7.2B11) deposited by magnetron sputtering onto a single-crystal langatate (La3Ga5.5Ta0.5O14) substrate. The langatate crystal was selected due to its favorable piezoelectric properties, high temperature stability, and absence of pyroelectric effects. Annealing significantly improved both the linear and nonlinear ME effects, resulting in a 7.6-fold increase in the linear ME coefficient, reaching 72 V/(Oe·cm), and a 15-fold enhancement in the nonlinear ME coefficient, reaching 610 mV/(Oe2·cm). The sensitivity of the structure increased accordingly by 7.6 times. The improvements observed are attributed to the uniformity of the magnetic domain structure and a decrease in the coercive force of the Metglas layer post-annealing. Magneto-optical Kerr microscopy confirmed the reduction of coercivity and revealed significant modifications in the magnetic domain structures after annealing, shifting the mechanism of magnetization reversal toward lower energy processes. TEM and XPS analyses indicated that annealing did not alter the amorphous state or composition of the Metglas film. The demonstrated approach of annealing offers a promising strategy for optimizing magnetoelectric properties in thin-film ME structures for advanced magnetic field sensing applications.