Preparation And Properties Of Multilayer Magnetic Thin Films,

Magnetoelectric(ME) composite materials have attracted researchers' durative interest due to the coupling among the electric,magnetic,and elastic order parameters and the ME effect,and one of the typical composite systems is Pb(Zr_0.52,Ti_0.48)O₃ /NiFe₂O_PZT/NFO.As the PZT has a large piezoelectric constant the NFO has a high permeability,the coupling effect is stronger than other oxide composite systems.In this paper,we firstly deposited single-layer PZT film on MgO substrate,and then studied the changes in ferroelectric induced by the different structures.Firstly,single-layer PZT,NFO/PZT and PZT/NFO/PZT multilayer thin films were deposited by PLD on MgO substrate with SRO bottom electrode,and the structure and ferroelectric property were studied roundly.And then a "sandwich" structure ME composite films of PZT/NFO/PZT and NFO/PZT/NFO were deposited on MgO substrate.The results Showed that the ferroelectric property were different as the sequence of deposition was different,and increasing thickness of NFO thin films have weakened the ferroelectric property of the PZT.Secondly,another ME composite film of PZT/NFO/PZT were deposited on STO substrate.Because of the difference of lattice constant between MgO and STO,Analysis indicated that the ferroelectric property of the composite film was different compared with PZT films deposited on MgO substrate while ferromagnetism could remain stable. It can be attributed to the interfacial strain and effect of SRO bottom electrode.Finally,The Fe₃O₄ ceramics was prepared by ball milling and sintering,then by the way of deposition in low- temperature and anneal in high- temperature,the best and optimized preparation parameter of Fe₃O₄ films'deposition on MgO substrate had been found,including oxygen pressure,substrate temperature,and so on.Analysis showed that different substrate temperature have influenced structure,resistance and ferromagnetism of thin films.On the basis of it,PZT/Fe₃O₄/MgO film was deposited.