Exchange-bias like hysteretic magnetoelectric-coupling of as-grown synthetic antiferromagnetic structures

The magnetoelectric (ME) coupling of CoFeB/Ru/CoFeB synthetic antiferromagnetic (SAF) structure is studied at room-temperature when the SAF structure was deposited on the (011)-Pb(Mg1/3Nb2/3)O3-PbTiO3 piezoelectric substrate. It was found that the magnetoelectric coupling showed butterfly like curve when measured in the absence of magnetic field but it showed hysteresis loop-like behavior as well as the exchange-bias like shift of the ME hysteresis under fixed magnetic fields of +250 Oe and +500 Oe. This exchange-bias like hysteretic ME coupling is attributed to the direct coupling of CoFeB layer with the substrate ferroelectric domain, the absence of magnetocrystalline anisotropy and the switching of 109 degree ferroelastic domains of the substrate. We have also measured the magnetoelectric coupling of CoFe/Ru/CoFe SAF structure but observed no exchange-bias like hysteresis behavior. Our results establish another way of obtaining the non-volatile memory devices based on magnetoelectric systems.