Memory effect of magnetoelectric coupling in antiferromagnetic cobalt tantalate with honeycomb lattice

Memory effect of magnetoelectric (ME) coupling is observed in antiferromagnetic Co 4 Ta 2 O 9 ME poling generated polarization below Néel temperature is retrieved after Co 4 Ta 2 O 9 is warmed to paramagnetic phase and then cooled to antiferromagnetic phase without being poled. This effect is ascribed to polar nanoregions in paramagnetic phase due to short range magnetic ordering as evidenced by temperature dependent magnetic entropy. If the applied magnetic field in paramagnetic phase is weakened, the memory effect is strengthened, which is ascribed to the less change of spin alignment induced by the weaker magnetic field. If we switch this magnetic field, the polarization when reentering polar phase is also reversed. Furthermore, the memory effect is also reflected in electric field dependent magnetization after the second cooling process without being poled.