Abstract
The integration of antiferroelectricity and ferromagnetism has been characterized as a novel performance in some special multiferroics, which could be designed for memories and energy storage purposes. Our study demonstrates that La modified M-type strontium hexaferrite (La0.2Sr0.7Fe12O19) has integrated such novel multiferroic features. By substituting 0.3 Sr 2+ ions with 0.2 La3+ ions in pure SrFe12O 19 so as to keep the charge balance, antiferroelectric state is switched on, being evidenced by double P-E hysteresis loops. The polarization saturated at 154 mC/cm 2 while the remnant polarization stays at 38 μC/cm2. The occurrence of antiferroelectrics is related to the the interruption of translational periodic symmetry by occupy of La atoms on Sr sites, which was verified by blue shift of the vibration bands to higher frequency side in Raman spectrum. The substitution lowers the Curie temperature for the phase transition from ferroelectric state to antiferroelectric one down to the vicinity of room temperature. The ferromagnetic hysteresis loop gives the values of remnant magnetic moment at 37.5 emu/g and coercive field at 4737 Oe, implying its strong magnetism. The X-ray photoelectron spectrometry (XPS) reveals the filling of ligating oxygen vacancy sites through oxygen heat-treatment and the enhancement in ferromagnetism is contributed from one additional unpaired 4f 1 electron spin in La 3+ . Therefore, the substitution of La3+ with Sr2+ in SrFe12O19 would not only transform it from ferroelectrics to antiferroelectrics, but could also improve its magnetic performance. This novel multiferroic feature combining antiferroelectrics and ferromagnetism could provide one more additional freedom to store energy by applying magnetic field.
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