Browsing by Author "Tian, H"

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    90° Rotation of orbital stripes in bilayer manganite PrCa2Mn2O7 studied by in situ transmission electron microscopy
    (Academic Press Inc Elsevier Science, 2013-04-01) He, ZB; Deng, G; Tian, H; Xu, Q; Van Tendeloo, G
    We present an in situ transmission electron microscopy study on the half-doped bilayer manganite PrCa2Mn2O7 to reveal the rotation process of the orbital stripes. Between the reported initial and final ordering phases, we identified an intermediate state with two sets of satellite spots to bridge the 90° rotation of the orbital stripes. Furthermore, we determined that the rotation of the orbital stripes does not always occur. Some restricted conditions for the orbital rotation to occur were found and reasons are discussed. © 2013, Elsevier Inc.
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    Characterisation of Fe distribution in the liquid–solid boundary of Al–Zn–Mg–Si alloy using synchrotron x-ray fluorescence microscopy
    (MDPI, 2024-07-17) Tian, H; Qu, DD; Setargew, N; Parker, DJ; Paterson, DJ; StJohn, D; Nogita, K
    Al–Zn–Mg–Si alloy coatings have been developed to inhibit the corrosion of cold-rolled steel sheets by offering galvanic and barrier protection to the substrate steel. It is known that Fe deposited from the steel strip modifies the microstructure of the alloy. We cast samples of Al–Zn–Mg–Si coating alloys containing 0.4 wt% Fe and directionally solidified them using a Bridgman furnace to quantify the effect of this Fe addition between 600 °C and 240 °C. By applying a temperature gradient, growth is encouraged, and by then quenching the sample in coolant, the microstructure may be frozen. These samples were analysed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) to determine the morphological effects of the Fe distribution across the experimental temperature range. However, due to the sub 1 wt% concentration of Fe, synchrotron X-ray fluorescence microscopy (XFM) was applied to quantitatively confirm the Fe distribution. Directionally solidified samples were scanned at 7.05 keV and 18.5 keV using X-ray fluorescence at the Australian Synchrotron using the Maia array detector. It was found that a mass nucleation event of the Fe-based τ6 phase occurred at 495 °C following the nucleation of the primary α-Al phase as a result of a peritectic reaction with remaining liquid. © 2024 The Authors. Licensee MDPI, Basel, Switzerland. - Open Access
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    Local magnetic structure at the Fe3O4/ZnO interface
    (Australian Institute of Physics, 2012-02-01) Brück, S; Paul, M; Tian, H; Müller, A; Fauth, K; Goering, E; Verbeeck, J; Van Tendeloo, G; Claessen, R
    Magnetite, Fe3O4, is a half-metal with 100% spin polarization of the minority band at the Fermi level. This together with its good conductivity match to standard semiconductors makes it a promising candidate for polarized spin injection into semiconductor materials such as Si, GaAs, or ZnO [1]. An important aspect for such applications is the magnetism directly at the interface between Fe3O4 and the semiconductor. Soft x-ray resonant magnetic reflectometry is a technique which is capable of providing structural and magnetic depth profiles with 0.1nm resolution. We present a detailed XRMR and electron energy loss spectroscopy (STEM/EELS) study of an epitaxial Fe3O4 thin film grown directly on a semiconducting ZnO substrate [2]. Consistent chemical profiles at the interface between ZnO and Fe3O4 are found from XRMR and EELS. The magnetic depth profile of tetragonal Fe3+ and octahedral Fe2+ ions in Fe3O4 is derived with monolayer resolution and reveals a change in the Fe stoichiometry directly at the interface.
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    Microstructure of bilayer manganite PrCa2Mn2O7 showing charge/orbital ordering
    (American Institute of Physics, 2013-05-27) He, ZB; Tian, H; Deng, G; Xu, Q; Van Tendeloo, G
    The microstructure of the charge/orbital ordering Ruddleden-Popper phase PrCa2Mn2O7 was studied by transmission electron microscopy along both the [001] and the [110] orientation. Three coexisting charge/orbital ordering phases CO1, CO2, and CO3 were observed along the [001] orientation at room temperature. Different from the one-dimensional modulation in the CO1 and CO2 phase, the CO3 phase is characterized by two sets of mutually perpendicular structural modulations. From [110] high angle annular dark field-scanning transmission electron microscopy, we found that the Pr atoms locate in-between the bilayer MnO6 octahedra, which is different from the previous reports. © 2013, American Institute of Physics.