Browsing by Author "Paull, O"
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- ItemCanted magnetism in modulated thin-film superlattices Oliver(Australian Institute of Nuclear Science and Engineering (AINSE), 2020-11-11) Paull, O; Wong., J; Sando, D; Lee, WT; Holt, SA; Valanoor, NInteractions at interfaces of magnetic materials such as giant magnetoresistance (GMR) form the physical foundation of many technological devices in today’s market. Although GMR technologies are now somewhat dated, interactions at the interface between layers of oxide materials continue to demonstrate attractive mechanisms for technology applications due to the wide variety of available oxide materials as well as their ability to be well lattice-matched to form heterostructures. Magnetic thin-film superlattices made of 15 repetitions of La2/3Sr1/3MnO3 (LSMO) and LaNiO3 (LNO) have been shown to exhibit a magnetic exchange interaction in LNO that is dependent upon its thickness n (where n is the number of unit cells of LNO) between LSMO layers [1]. At n = 1, the LSMO layers are ferromagnetically aligned with eachother. At n = 3 however, the LSMO layers are canted by 110◦ with respect to one another. This canting is reportedly driven by an emergent c-axis spin-helix in LNO that arises due to charge transfer at the interfaces between LNO and LSMO [2]. We have fabricated superlattices of similar quality to Ref. [1] using Reflected High Energy Electron Diffraction (RHEED) assisted Pulsed Laser Deposition (PLD), where RHEED is used to ensure unit-cell precision in layer thicknesses. These superlattices have been designed so they exhibit n = 3 and n = 1 interactions within the same superlattice in a modulated pattern. This modulation of the effective LNO exchange interaction in these samples creates a toy model of coupled magnetic layers to explore. The modulated design of these samples create “frustrated” environments where the effective exchange interaction is different on each side of an LSMO layer within the superlattice. We utilise polarised neutron reflectometry using PLAYPUS to reveal the complex magnetic profile of these modulated superlattices by measuring the non-spin-flip (R++, R−−), and spin-flip (R+−, R−+) cross sections. Presented are the current progress and prospects in the fitting process of these complex datasets. © The authors.
- ItemMagnetic proximity effect in YBCO/STO/LCMO multilayers(Australian Institute of Physics, 2017-01-31) Paull, O; Causer, GL; Pan, AV; Klose, FTailoring of the electronic properties of complex oxide heterostructures, thin films, and superlattices with atomically sharp interfaces is at the frontline of materials research at present [1, 2, 3]. Interfaces exhibit novel states that are not possible in bulk materials as a result of broken symmetry, induced strains, and modified exchange interactions. In this work we examined the interaction between a superconducting YBa2Cu3O7-δ thin film layer and a ferromagnetic La2/3Ca1/3MnO3 layer using polarised neutron reflectometry. The interaction at the interface between YBCO/LCMO multilayers has resulted in a variety of observed phenomena such as induced ferromagnetic moments in YBCO layers that are antiparallel to neighbouring LCMO layers, and a strong reduction in magnetization in LCMO near the interface. Prajapat et al. investigated the YBCO/LCMO interface using SrTiO3 (STO) as an intermediate insulating layer, and reported that the magnetic depletion (MD) in LCMO near the interface is dependent on the critical temperature of YBCO and the thickness of the LCMO layer, and claimed that the origin of the MD in LCMO is due to Cooper pairs tunneling through the STO interlayer across the interface [5]. Our work has verified the observation of the MD layer in LCMO near the interface as claimed in the past report, and additionally studied the effect of a magnetic field on this layer. Polarised neutron reflectometry measurements performed at ANSTO on the PLATYPUS reflectometer indicate that the effect of applying fields at 0.03 T and 1 T is to cause a small restoration of magnetization in this depleted layer. This result supports the mechanism proposed by Prajapat et al. of a superconductivity-induced MD from tunneling through STO.
- ItemMagnetic proximity effect in YBCO/STO/LCMO multilayers(Australian Institute of Nuclear Science and Engineering, 2016-11-29) Paull, O; Causer, GL; Pan, AV; Klose, FTailoring of the electronic properties of complex oxide heterostructures, thin films, and superlattices with atomically sharp interfaces is at the frontline of materials research at present [1, 2, 3]. Interfaces exhibit novel states that are not possible in bulk materials as a result of broken symmetry, induced strains, and modified exchange interactions. In this work we examined the interaction between a superconducting YBa2Cu3O7-δ thin filmlayer and a ferromagnetic La2/3Ca1/3MnO3 layer using polarised neutron reflectometry. The interaction at the interface between YBCO/LCMO multilayers has resulted in a variety of observed phenomena such as induced ferromagnetic moments in YBCO layers that are antiparallel to neighbouring LCMO layers, and a strong reduction in magnetization in LCMO near the interface. Prajapat et al. investigated the YBCO/LCMO interface using SrTiO3(STO) as an intermediate insulating layer, and reported that the magnetic depletion (MD) in LCMO near the interface is dependent on the critical temperature of YBCO and the thickness of the LCMO layer, indicating that the origin of the MD in LCMO is due to Cooper pairs tunneling through the STO interlayer across the interface [5]. Our work has verified the observation of the MD layer in LCMO near the interface as claimed in the past report, and additionally studied the effect of a magnetic field on this layer. Polarised neutron reflectometry measurements performed at ANSTO on the PLATYPUS reflectometer indicate that the effect of applying fields at 0.03 T and 1 T is to cause a small restoration of magnetization in this depleted layer. This result supports the mechanism proposed by Prajapat et al. of superconductivity-induced MD from tunnelling through STO.