| Low-dimensional magnetic materials have attracted extensive attention due to their potential applications in sensors,nonvolatile memory,spintronic devices.Magnetic anisotropy is one of the important properties of low-dimensional magnetic material and underlies many of these applications.Consequently,the mediation of magnetic anisotropy in low-dimensional magnetic material is of great importance.Among these materials,epitaxial metallic magnetic thin films have been widely investigated because of their excellent properties.Strain-induced magnetic anisotropy is a useful method to mediate the magntiec properties of epitaxial metallic magnetic thin films.In this article,high epitaxial Ni thin films were prepared by magnetronsputtering.The mechanism of the modulation for the magnetic anisotropy in differentoriented Ni thin films has been investigated in detail.The main results are shown as follows:(1)Ni thin films with face-centered cubic structure were prepared on(001)oriented STO single crystal substrates by magnetron sputtering.The optimal processing parameters were acquired as follows:The substrate temperature was 500 ? and the deposition pressure was 0.5 Pa.The target base distance was fixed at 50 mm while the sputtering power was maintained at 60 W.After deposition,the film was in-situ annealed at 500 ? for 30 minutes.X-ray diffraction(XRD)results show that the films were grown preferentially along the(001)plane with high crystallinity and lower full width at half maximum(FWHM).The results of AFM and XRR experiments show that the surface of the film was smooth and uniform with lower surface roughness.The results of magnetic properties indicate that the film has good ferromagnetism for in-plane and out-of-plane magnetic anisotropy at room temperature.(2)Using optimal growth parameters,(001),(110),(111)oriented epitaxial Ni thin films were prepared on different orientations of PMN-PT single crystal substrates.The XRD diffraction pattern shows that the Ni thin films were epitaxial grown along the substrate orientation.The results of AFM and XRR indicate that the films were uniform and the thickness was calculated as about 25 nm.The strains of three different oriented films were calculated by using XRD results.It is obvious that compressive strain occurs in the thin film along OOP direction while tensile strain occurs along IP direction.Hysteresis loops of the three epitaxial films show that the(111)oriented film has the strongest magnetic anisotropy and the(001)oriented film has stronger magnetic anisotropy than the(110)oriented one.The calculations indicate that the stress-induced magnetoelastic energy increased the anisotropy field and reduced the free energy,resulting in(001)-oriented one has a higher magnetic anisotropy compared to(110)oriented one.The substrate has piezoelectricity,electric field was applied to the(110)-oriented sample.The magnetic anisotropy of the film was dominated by the magnetoelectric coupling effect of the interface.Since there is a lattice mismatch between the thin film and the single crystal substrate,the magnetic anisotropy of the Ni thin film can be changed by regulating the strain state of the thin film.Using optimal growth parameters,Ni thin films were prepared on the(001)oriented LaAlO3(LAO),PMN-PT,MgA12O4(MAO),and MgO single crystal substrates.XRD results shows that the Ni thin films grown on the four different substrates maintain preferential orientation growth with the substrate,and all the films have excellent crystallinity.The results of the AFM and XRR show that the surfaces of the thin films are uniform,and the thickness is 30 nm.According to the XRD results,the strain states of the films grown on four different types of substrates are analyzed.The in-plane and out-of-plane hysteresis loops at room temperature of the four samples demonstrate that the magnetization state of the film has a strong dependence on the strain state.These results indicate that the magnetic anisotropy of the epitaxial film can be controlled by biaxial strain.It provides useful method to control the magnetic properties of matellic magnetic films in microelectronic devices.(3)Ni thin films were prepared on a(001)-oriented PMN-PT single crystal substrate by magnetron sputtering.Ta buffer layer was inserted between the thin film and the substrate,the inherent stress of the thin film is released.Both the in-plane and out-of-plane directions exhibit strong magnetic anisotropy.As the Ta buffer layer thickness increases,the crystal structure changes and magnetic anisotropy decreases.The SrRuO3(SRO)buffer layer was also prepared by Pulsed Laser Deposition(PLD)between Ni thin films and substrate.The SRO buffer layer could bring about interfacial effect,resulting in increasing the interfacial dislocation between the Ni thin films and the substrate.Different strain states affected the saturation magnetization of the magnetic anisotropy.With the increase of the thickness of the buffer layer,themagnetic anisotropy increases.The above experimental results will provide useful understanding in the magnetic anisotropy of the matellic magnetic film,and also provide new experimental ideas for controlling the magnetic anisotropy... |
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