Abstract
The chemical asymmetry at the hetero-structure interface offers an effective opportunity to design desirable electronic structures by controlling charge transfer and orbital hybridization across the interface. However, controlling the hetero-interface remains a daunting task. Here, we report the modulation of interfacial coupling of (La0.67Sr0.33MnO3)n/(SrTiO3)n superlattices by manipulating the periodic thickness with n unit cells of SrTiO3 and n unit cells of La0.67Sr0.33MnO3 with a fixed thickness of ~120 unit cells. The easy axis of magnetic anisotropy rotates ~45° towards the out-of-plane direction from n = 10 to n = 2 at reduced temperature TRe = T/TS = 0.87, where TS is the temperature at the onset of magnetization. Transmission electron microscopy reveals an enlarged tetragonal ratio >1 with breaking of volume conservation around the (La0.67Sr0.33MnO3)n/(SrTiO3)n interface and electronic charge transfer from Mn to Ti 3d orbitals across the interface. Orbital hybridization accompanying the charge transfer results in preferred occupancy of {3d}_{3z^2-r^2} orbitals at the interface and induces a stronger electronic hopping integral and interfacial magnetic anisotropy along the out-of-plane direction, which contributes to the rotation towards the out-of-plane direction of an effective magnetic easy axis for n = 2. We demonstrate that interfacial orbital hybridization with charge transfer in the superlattice of strongly correlated oxides may be a promising approach to tailor electronic and magnetic properties in device applications.
Highlights
The asymmetry at the heterostructure interface of 3d transitional metal ABO3 oxides, including the mismatch of lattice constant, oxygen octahedral rotation and distortion, and chemical environment, has profound influences on spin and orbital coupling, yielding emerging phenomena such as enhanced ordering temperature, induced interfacial magnetism at the superconductor/Zhang et al NPG Asia Materials (2018) 10: 931-942 discontinuity, of the ABO3 perovskite heterostructure interface may be exploited to study the effect of charge transfer and crystal structure[26–28].Recent work[13] claimed that oxygen octahedral coupling (OOC) is the leading factor affecting orbital hybridization in ultrathin manganite film; the effect of charge transfer on magnetic properties is important[6–11]
The final distribution of planar charge is illustrated as a pink bar at the right bottom of Fig. 1a, and the short-range charge transfer is constrained to several unit cells (UCs) near the interface[32–35], illustrated as the probability of charge transfer at the left bottom of Fig. 1a
A different reference temperature TS is introduced for analysis, defined as the temperature at which magnetization of the material starts to appear
Summary
The asymmetry at the heterostructure interface of 3d transitional metal ABO3 oxides, including the mismatch of lattice constant, oxygen octahedral rotation and distortion, and chemical environment, has profound influences on spin and orbital coupling, yielding emerging phenomena such as enhanced ordering temperature, induced interfacial magnetism at the superconductor/Zhang et al NPG Asia Materials (2018) 10: 931-942 discontinuity, of the ABO3 perovskite heterostructure interface may be exploited to study the effect of charge transfer and crystal structure[26–28].Recent work[13] claimed that oxygen octahedral coupling (OOC) is the leading factor affecting orbital hybridization in ultrathin manganite film; the effect of charge transfer on magnetic properties is important[6–11]. The interfacial coupling of (LSMO)n/(STO)n superlattices (SLs) is manipulated by controlling the periodic thickness with n UCs of STO and n UCs of LSMO with a fixed thickness of ~120 UCs. The easy axis of magnetic anisotropy rotates ~45° towards the out-of-plane direction from n = 10 to n = 2 at reduced temperature TRe = T/TS = 0.87, where TS is the onset point of magnetization.
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