Exchange-spring mechanism and Griffiths-like phase in room-temperature magnetoelectric Ni-BaTiO3 composites

Magnetoelectric composite materials consisting of coupled magnetic and ferroelectric phases open doors to exciting applications like electrically controlled magnetic sensors and memories. In this direction, we report the first-time observation of the exchange-spring mechanism in nickel-barium titanate magnetoelectric composite systems. The low field DC magnetization measurements of the Ni-BaTiO3 composite systems reveal an anomalous magnetic behaviour indicating the presence of a Griffiths-like phase. The exchange bias loop shift observed in the Ni-BaTiO3 systems confirms the formation of antiferromagnetic NiO. The structural transitions of BaTiO3 visible in the magnetic data implicate magnetoelectric coupling between Ni and BaTiO3. The maximum value of the magnetoelectric coupling coefficients observed for the Ni-BaTiO3 0-3 composites is 18.53 mV cm Oe(-1), and for the composites with 1-3 connectivity it is 10.91 mV cm Oe(-1); both values are higher than the reported values of Ni-BaTiO3 particulate composites. In addition to this, the magnetoelectric coupling coefficients of the Ni-BaTiO3 composites with 1-3 connectivity show an increasing trend towards the BaTiO3 rich composite.