The fabrication of well‐defined, atomically sharp substrate surfaces over a wide range of lattice parameters is reported, which is crucial for atomically regulated epitaxial growth of complex oxide heterostructures. By applying a framework for controlled selective wet etching of complex oxides on the stable rare‐earth scandates (REScO3), apseudocubic = 0.394 – 0.404 nm, the large chemical sensitivity of REScO3 to basic solutions is exploited, which results in reproducible, single‐terminated surfaces. Time‐of‐flight mass‐spectroscopy measurements show that after wet etching the surfaces are predominantly ScO2 ‐terminated. Moreover, the morphology study of SrRuO3 thin‐film growth gives no evidence for mixed termination. Therefore, it is concluded that the REScO3 surfaces are completely ScO2 ‐terminated.

Obtaining atomically smooth surfaces and interfaces of perovskite oxide materials on polar (111) surfaces presents a particular challenge as these surfaces and interfaces will reconstruct. Here, the effect of the use of screening buffer layers on the epitaxial growth on such polar surfaces is investigated. Both transmission electron microscopy and in situ reflective high energy electron diffraction data imply that the buffer layers, SrRuO3 or LaAlO3, restore a near bulk-like termination at growth temperature, allowing for coherent growth of BiFeO3 and CaTiO3 for all deposited unit cell layers of the film material.

Abstract

We present first-principles calculations of the structural phase behavior of the [1:1] PbTiO3/PbZrO3 superlattice and the PbTiO3 and PbZrO3 parent compounds as a function of in-plane epitaxial strain. A symmetry analysis is used to identify the phases and clarify how they arise from an interplay between different kinds of structural distortions, including out-of-plane and in-plane polar modes, rotation of oxygen octahedra around out-of-plane or in-plane axes, and an anti-polar mode. Symmetry-allowed intermode couplings are identified and used to elucidate the nature of the observed phase transitions. For the minimum-period [1:1] PbTiO3/PbZrO3 superlattice, we identify a sequence of three transitions that occur as the in-plane lattice constant is increased. All four of the phases involve substantial oxygen octahedral rotations, and an antipolar distortion is important in the high-tensile-strain phase. Inclusion of these distortions is found to be crucial for an accurate determination of the phase boundaries.

We report time-resolved Kerr effect measurements of magnetization dynamics in ferromagnetic SrRuO3. We observe that the demagnetization time slows substantially at temperatures within 15K of the Curie temperature, which is ∼ 150K. We analyze the data with a phenomenological model that relates the demagnetization time to the spin flip time. In agreement with our observations the model yields a demagnetization time that is inversely proportional to T-Tc. We also make a direct comparison of the spin flip rate and the Gilbert damping coefficient showing that their ratio very close to kBTc, indicating a common origin for these phenomena. I: IntroductionThere is increasing interest in controlling magnetism in ferromagnets. Of particular interest are the related questions of how quickly and by what mechanism the magnetization can be changed by external perturbations. In addition to advancing our basic understanding of magnetism, exploring the speed with which the magnetic state can be changed is crucial to applications such as ultrafast laser-writing techniques. Despite its relevance, the time scale and mechanisms underlying demagnetization are not well understood at a microscopic level.Before Beaurepaire et al.'s pioneering work on laser-excited Ni in 1996, it was thought that spins would take nanoseconds to rotate, with demagnetization resulting from the weak interaction of spins with the lattice. The experiments on Ni showed that this was not the case and that demagnetization could occur on time scales significantly less than 1 ps 1 . Since then demagnetization is usually attributed to Elliott-Yafet mechanism, in which the rate of electron spin flips is proportional to the momentum scattering rate. Recently Koopmans et al. have demonstrated that electron-phonon or electron-impurity scattering can be responsible for the wide range of demagnetization time scales observed in different materials 2 . Also recently it has been proposed that electron-electron scattering should be included as well as a source of Elliott-Yafet spin flipping, and consequently, demagnetization 3 . Although Ref.3 specifically refers to interband scattering at high energies, it is plausible that intraband electron scattering can lead to spin memory loss as well. Time-resolved magneto-optical Kerr effect (TRMOKE) measurements have been demonstrated to be a useful probe of ultrafast laser-induced demagnetization 1 . In this paper we report TRMOKE measurements on thin films of SRO/STO(111) between 5 and 165K. Below about 80 K we observe damped ferromagnetic resonance (FMR), from which we determine a Gilbert damping parameter consistent with earlier measurements on SrTiO 3 with (001) orientation 6 . As the the Curie temperature (∼ 150K) is approached the demagnetization time slows significantly, as has been observed in other magnetic systems 4 . The slowing dynamics have been attributed to critical slowing down, due to the similarities between the temperature dependencies of the demagnetization time and the relaxation time 5 . In this paper we devel...