Preparation And Properties Of NiFe/BaTiO₃/La_0.7Sr_0.3MnO₃ Multiferroic Tunnel Junction At Room Temperature

With the development of the Internet,large data and cloud computing,we have come to an era of information explosion,the amount of global information goes to order of magnitude 1021 bits and the date would double every three years,it puts forward higher requirement on storage capacity.Multiferroic tunnel junctions as a new type of polymorphic storage device,the magnetoelectric coupling effect will lead to higher density,lower power consumption and electric field controllable magnetic read and write memory and nearly a decade over the past few years theoretical and experimental research of multiferroic tunnel junction has made great progress,which makes people see more great application prospect.In this paper,NiFe/BTO₃/La_0.7Sr_0.3MnO₃ multiferroic tunnel junctions are choosed as the study object.Firstly the background,application and existing main problems are introduced.Then the performance of the ferromagnetic layer La_0.7Sr_0.3MnO₃?LSMO?and ferroelectric layer of BaTiO₃?BTO?were studied systematically and respectively.The main contents and results of this paper are summarized as follows:1.Firstly,the substrates SrTiO₃?STO?were treated to TiO₂-terminated single end surface with solution mixed with NH4 F and HF and annealed in tube type furnace with 950 oC high temperature for 75 mins.The surface morphology of etched substrates were characterized by AFM to eliminate the influence of the original topography of substrates.The experimental results showed that: the etched surface of the substrates will form steps and the height between steps is 0.4 nm which is about a layer of cell thickness.It can be used for high quality epitaxial films.2.LSMO was achieved on STO substrate by pulse laser deposition?PLD?method under different substrate temperature and oxygen partial pressure and the surface morphology and performance was characterized subsequently.The results indicated that oxygen partial pressure has a great influence on the Curie temperature and surface morphology.Especially under relatively higher oxygen partial pressure of0.3 mbar the films Curie temperature is approaching bulk Curie temperature?³60 K?,and the magnetization of LSMO can reach 1.6 ± 0.11 ? B pure Mn atoms,the surface roughness of the samples is about 350 pm which can achieve goodrequirements of the epitaxial film at room temperature.However,substrate temperature has less effect on the Curie temperature shift points and the surface morphology has a bigger change in 750 oC.3.The ferroelectric material of BaTiO₃?BTO?was grew on LSMO using PLD method and the butterfly loop and electric hysteresis loop were measured by PFM method subsequently.Then 10 hours retentivity was also tested.The results indicated that: the grown BTO has a good performance in electric hysteresis loop and butterfly loop and Amplitude image and Phase figure showed that BTO have a good retentivity.4.NiFe/BaTiO₃/La_0.7Sr_0.3MnO₃ multiferroic tunnel junctions were achieved through photolithography?Plasma Enhanced Chemical Vapor Deposition?PECVD??magnetron sputtering and micro-nano processing and the performance were characterized...