Ba0.8Sr0.2TiO3/CoFe2O4异质结层状多铁复合薄膜的制备与性能

摘要

利用射频磁控溅射法在Pt(200)/TiO2/SiO2/Si(100)衬底上沉积Ba0.8 Sr0.2TiO3/CoFe2O4异质结层状多铁磁电耦合复合薄膜.Ba0.8Sr0.2TiO3/CoFe2O4异质结复合薄膜为多晶,由钙钛矿Ba0.8Sr0.2TiO3相和尖晶石CoFe2O4相组成.复合薄膜表现为良好的铁电性和铁磁性共存.在测量磁场平行于样品表面情况下测得的复合薄膜的饱和磁化强度(Ms)、剩余磁化强度(Mr)值要大于在测量磁场垂直于样品表面时测得的Ms、Mr值.另外,复合薄膜具有直接的磁电耦合效应,磁电电压系数αE先随着偏置磁场H dc的增大而增大,当偏置磁场H dc增加到445.8 kA/m后,αE反而随偏置磁场的增加而减少.当偏置磁场Hdc=445.8 kA/m时,复合薄膜具有最大的磁电电压系数αE=18.8 mV/A.%A Ba0.8Sr0.2TiO3/CoFe2O4 heterostructure composite film was grown on a Pt (200 )/TiO2/SiO2/Si (100) substrate by RF-magnetron sputtering.X-ray diffraction shows that the composite film consists of per-ovskite Ba0.8Sr0.2TiO3 and spinel CoFe2O4 phases.The microstructure of the composite film was observed by a field-emission scanning electron microscope,showing clear interfaces among the Ba0.8 Sr0.2TiO3 film,CoFe2O4 film and the substrate.The value of the leakage current density for the composite film is 3.1×10-5 A/cm2 at the electric field of about 100.0 kV/cm.The variations of dielectric properties with frequency of the heterostructure composite film are investigated.In the region of low frequency,dielectric constant sharply decreases with the in-crease of frequency,while in the region of higher frequency,dielectric constant is almost constant,exhibiting dielectric dispersion.The composite film simultaneously displays distinct ferroelectricity and ferromagnetism. The values of saturated polarization (2Ps),remnant polarization (2Pr) and coercive electric field (2Ec) of the composite film are 38.2,9.8μC/cm2 and 260.1 kV/cm,respectively.The saturated magnetization (Ms ) and remnant magnetization (Mr) of the composite film measured in the applied magnetic field parallel to the surface of the sample are larger than those measured in the applied magnetic field perpendicular to the surface of the sample.Moreover,an obvious direct magnetoelectric coupling effect was observed in the heterostructure com-posite film.Magnetoelectric voltage coefficient (αE ) increases with the increase of applied magnetic field,then when the applied magnetic field increases to 445.8 kA/m,on the contrary,αE decreases with the increase of ap-plied magnetic field.The maximumαE is 18.8 mV/A at the applied magnetic field of 445.8 kA/m.