Synergetic Control Of Magnetic Anisotropy In Freestanding SrRuO₃ Films By Crystal Orientation And Structure

With the rapid development of flexible electronic devices with excellent flexural and tensile properties,people are paying more attention to the exploration of flexible materials.The transition metal oxide SrRuO₃ with perovskite structure has good metal conductivity,strong magnetocrystalline anisotropy as well as strong spin orbit coupling（SOC）interaction,which is widely considered as an important spintronic material.In the field of flexible spintronics,the realization of high-quality preparation of flexible SrRuO₃ and effective control of its magnetic anisotropy will be of great benefit to its application in the fields of flexible storage and sensing.Based on these characteristics,SrRuO₃ thin films with(Ca_0.5Sr_0.5)₃Al₂O₆ or Sr₃Al₂O₆ water-soluble sacrificial layers were grown on Sr Ti O₃ with[001],[110]and[111]orientations respectively.And then SrRuO₃ single crystal thin films were deposited in order to achieve high-quality preparation of flexible freestanding SrRuO₃ films with different crystal orientations.The phase structure,surface morphology and magnetic anisotropy of SrRuO₃ thin films were characterized by high resolution X-ray diffraction,reflection high energy electron diffraction,scanning probe microscope and superconducting quantum interference device.Combined with crystal orientation and structure,the magnetic anisotropy of flexible freestanding SrRuO₃ thin films is effectively controlled.Firstly,crystal orientation control of magnetic anisotropy of orthorhombic SrRuO₃ freestanding thin films was studied.The(Ca_0.5Sr_0.5)₃Al₂O₆and SrRuO₃ thin films were grown on Sr Ti O₃ substrates with three orientations in turn.The freestanding SrRuO₃ thin films with orthorhombic structure were constructed.After the SrRuO₃thin films with three crystal orientations are exfoliated,the crystal plane spacing d in the vertical direction of the lattice decreased to 3.930（?）,2.784（?）and2.265（?）respectively.Before and after being exfoliated,SrRuO₃ films with three crystal orientations are easier to be magnetized along the out of plane direction.After being exfoliated,the magnetic anisotropy energy of SrRuO₃ films with three crystal orientations decreased to 1.58×10⁶erg/cm³,7.31×10⁶erg/cm³and 2.16×10⁶erg/cm³.Secondly,crystal orientation control of magnetic anisotropy of tetragonal SrRuO₃ freestanding thin films was investigated.Sr₃Al₂O₆ and SrRuO₃ thin films were grown on Sr Ti O₃ substrates with three orientations in turn.The freestanding SrRuO₃ thin films with tetragonal structure were constructed.After the SrRuO₃thin films with three crystal orientations are exfoliated,the crystal plane spacing d in the vertical direction of the lattice increased to 3.927（?）,2.772（?）and 2.279（?）respectively.Before and after being exfoliated,[001]-SrRuO₃film was easier to be magnetized along the out of plane direction,and its magnetic anisotropy energy decreased from5.27×10⁶erg/cm³to 2.54×10⁶erg/cm³.[110]-SrRuO₃film and[111]-SrRuO₃film were easier to be magnetized along the in-plane direction.The magnetic anisotropy energy of[110]-SrRuO₃film decreased from 6.38×10⁶erg/cm³to 6.05×10⁶erg/cm³.The magnetic anisotropy energy of[111]-SrRuO₃film increased from 3.26×10⁶erg/cm³to4.52×10⁶erg/cm³.Finally,mechanism of orientation and structure controlling magnetic anisotropy of SrRuO₃freestanding film was researched.Combined with the theoretical calculation,it is further proved that the orbital occupancy state of SrRuO₃ is effectively controlled by controlling the crystal orientation and structure.Taking the[111]orientation as an example,for the orthorhombic phase,the e_g and t_2g orbitals of the d electrons of Ru atoms maintained a high degree of degeneracy;When the structure changes to tetragonal phase,their degeneracy decreased and the split occurred.The change of orbital degeneracy caused by this structural phase transition leads to the significant change of the interaction between d_xy and d_xz and d_yz,which further regulated the magnetic anisotropy,orthorhombic SrRuO₃ is easier to be magnetized along the out of plane direction,while tetragonal SrRuO₃ is easier to be magnetized along the in-plane direction.