The Transport Property And Electric Control Of Multiferroic Heterostructures

How to control the spin to write the information is one of the most important researches with the application of spintronics in the field of information.Up to now,the electric field,optical field,magnetic field,and current are used to manipulate the spin.The multiferroic materials have attracted much attention in the field of electric control spintronics with low-energy and nonvolatile due to magnetoelectric coupling effects.In this thesis,the electric control spin transport and magnetism in oxide multiferroic heterostructures have been studied,which may offer insights for the electric control spintronics.The main researches of my thesis are listed as follows.(1)The BiFeO3/SrRuO3(BFO/SRO)heterostructures were epitaxially grown by pulsed laser deposition.The SRO shows topological Hall effect-like(THE-like)around the polarity transition temperature of anomalous Hall effect(AHE).Combining the phenomenological analysis,the THE-like is originated from the superposition of AHE with positive and negative polarity induced by inhomogeneous SRO layer.Furthermore,the magnitude and polarity of AHE in the BFO/SRO structure can be manipulated by switching the ferroelectric polarization of BFO via voltage.The modulation of AHE in SRO under ferroelectric polarization was discussed by first-principles calculation,which originates from the change of band structure around the Fermi level.(2)The PbZr0.2Ti0.8O3/Co/Pt(PZT/Co/Pt)hetero structures were grown by pulsed laser deposition and magnetron sputtering.The perpendicular magnetic anisotropy(PMA)of the PZT/Co/Pt structure can be modulated by switching the polarization field of the PZT layer with reversible and nonvolatile.Moreover,the modulation of PMA arises from the change of the hybridization between Co and O orbitals at the PZT/Co heterointerface induced by polarization.At zero magnetic field,the anomalous Hall resistance of heterostructure under polarization away PZT/Co interface is higher than that under polarization toward PZT/Co interface.Furthermore,the spin memory and logic devices are proposed based on the ferroelectric-modulated anomalous Hall resistance.(3)The SrIrO3(SIO)thin film and SIO/PZT heterostructures were epitaxial grown by pulsed laser deposition.Large magnetoresistance was observed in SIO and SIO/PZT with the magnetic field applied perpendicular to the current at low temperature.In addition,the SIO/PZT bilayer shows the negative magnetoresistance with oscillations when the magnetic field is parallel to current at 1.8 K.According to the angular,magnetic field and temperature dependence magnetoresistance and theory analysis,we believe that the large magnetoresistance is from the Dirac point near the Fermi level.