Research On Magnetic Properties Of Iron Garnet Films Prepared By Pulsed Laser Deposition

With the development of spintronics,it has been found that the insulating magnetic garnet films with perpendicular magnetic anisotropy(PMA)has a lot of excellent properties,which meets the requirement of smaller,faster and more efficient electronic devices greatly.It is reported that the spin-orbit-torque(SOT)effect in heavy metal or topological insulator/magnetic layer heterostructure could be used to manipulate the magnetic moment much more energy efficiently than the spin-transfer-torque(STT)in conventional magnetic tunnel junction structure.And the ultra-thin magnetic insulating film with thickness less than 100 nm has stronger interface effect,which greatly reduces the loss,miniaturizes the devices,and improves the storage density.At present,from the perspective of basic research on spin pumping effect and the application of practical devices such as spin torque oscillator,it is of great significance to prepare high quality,ultra-thin,low damping constant and high stability magnetic insulating films.The purpose of this paper is to prepare ultra-thin garnet films with PMA and low damping constant.Tm3Fe5O12 film,Bi1Tm2Fe5O12 film,Y3Fe5O12 film,the Bi-doped yttrium iron garnet film were epitaxially grown on single crystal GGG and SGGG substrates by PLD.And The structure and magnetic properties of the film were tested and analyzed.In the first part,Tm3Fe5O12 films with thickness of 60 nm were extensional grown on GGG and SGGG substrates by PLD.It was found that Tm3Fe5O12/GGG films was subjected to compressive stress,the easy magnetization axis was in-plane,and Tm3Fe5O12/SGGG films were subjected to tensile stress.The easy magnetization axis appears to be out-of-plane.By changing the stress between the film and the substrate,the stress-induced anisotropy was used to overcome the shape anisotropy of the film,and then the PMA of the film was induced.Finally,Tm3Fe5O12/SGGG film with PMA and damping constant ?=1.179×10-2 was prepared.In the second part,Bi1Tm2Fe5O12 films with thickness of 60 nm were grown on GGG and SGGG substrates respectively.It is found that the easy magnetization axis of Bi1Tm2Fe5O12/GGG film is still in-plane,and the uniaxial anisotropy induced by bismuth doping is not enough to overcome the shape anisotropy.However,the magnetization axis of Bi1Tm2Fe5O12/SGGG thin film is out-of-plane,and the damping constant ?=1.158×102 is similar to that of Tm3Fe5O12/SGGG thin film,indicates that the doping of Bi3+ions reduces the lattice mismatch between the film and the substrate,and reduces the damping coefficient of the film.In the third part,Y3Fe5O12 films with thickness of 60 nm were epitaxial grown on GGG and SGGG substrates respectively.It was found that the easy magnetization axes of YIG/GGG and YIG/SGGG films were both in-plane,and YIG/GGG film had low damping constant.The damping constant of YIG/GGG films in the in-plane direction is?=2.49×10-3.In the fourth part,Bi0.7Y2.3Fe5O12 films with thickness of 60 nm were epitaxial grown on GGG and SGGG substrates,respectively.It was found that the easy magnetization axes of Bi:YIG/GGG and Bi:YIG/SGGG were both in-plane and the damping coefficient of Bi:YIG/SGGG films was lower than that of YIG films.