Browsing by Author "Pan, AV"
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- ItemEnhancement of co substitution induced by Eu codoping in ZnO-based diluted magnetic semiconducting thin films(American Institute of Physics, 2010-02) Photongkam, P; Zhang, YB; Assadi, MHN; Li, S; Yu, DH; Ionescu, M; Pan, AVTo avoid the occurrence of doped magnetic ion clustering is a challenge in fabrication of diluted magnetic semiconductors (DMSs). In this work, we report the intrinsic ferromagnetic behavior in Co-doped ZnO DMSs induced by Eu codoping. Both structural parameters and magnetic properties demonstrate the existence of an interaction between Co and Eu ions. The observation of multiplet structures for the localized Co 3d states in x-ray absorption and x-ray magnetic circular dichroism characterization evidences that the codoped Eu plays an important role in facilitating the Co substitution of Zn, leading to intrinsic ferromagnetism. © 2010, American Institute of Physics
- ItemInvestigations into the controllable change of Curie temperature in silver doped lanthanum manganite nanoparticles(Australian Institute of Nuclear Science and Engineering, 2016-11-29) Westlake, M; Lerch, MLF; Konstantinov, K; Rule, KC; Yu, DH; Pan, AV; Cardillo, D; Horvat, J; Tehei, MOur team is focused on research into the design, production, characterisation and implementation of optimized nanostructured particles for principally the diagnosis (as CT and MRI contrast agents) and treatment of cancer (using radiation, oncothermia and hyperthermia modalities). One magnetic nanoparticle of current interest is Lanthanum Manganite (LaMnO3) and its silver doped counterpart (La1-xAgxMnO3). The high effective atomic number and magnetic moment of LaMnO3 [1] makes this material appropriate for the basis of an MRI and CT contrast agent and enhancing radiation therapies. In addition La1-xAgxMnO3 is also considered as a good candidate for hyperthermia cancer therapy [2].For the characterization of our samples we used XRD, PPMS, SEM, EDS and SEM. We observed that the Curie temperature increased with the increase of the silver doping concentration in the nanoparticles. This has led to an investigation into the mechanism behind this change. The spin-phonon interaction was considered to represent one potential mechanism and Time of Flight measurements where conducted on PELICAN at ANSTO. A lack of phonon evolution was seen within the temperature range of 1.5K - 300K. In order to access phonon density of states over a broader range of energies, we are then planning to use the Beryllium filter on TAIPAN and scan through a wide energy range while measuring scattered neutron over a vastly increased solid angle. The following poster will focus on the characterizations of our samples, our first experiments on PELICAN and our future planed experiments in the aim to better understand the mechanism that provokes the change of Curie temperature upon silver doping.
- ItemMagnetic field dependent neutron powder diffraction studies of Ru0.9Sr2YCu2.1O7.9(American Institute of Physics, 2010-05-01) Nigam, R; Pan, AV; Dou, SX; Kennedy, SJ; Studer, AJ; Stuesser, NTemperature and magnetic field dependent neutron diffraction has been used to study the magnetic order in Ru0.9Sr2YCu2.1O7.9. The appearance of (1/2, 1/2, 1/2), (1/2, 1/2, 3/2), and (1/2, 1/2, 5/2) peaks below TM = 140 K manifests the antiferromagnetic order. Neutron diffraction patterns measured in applied magnetic fields from 0 to 6 T show the destruction of the antiferromagnetic order with increasing field. There is no evidence of spontaneous or field-induced long range ferromagnetic order. This latter result contradicts the vast majority of other experimental observations for this system. © 2010, American Institute of Physics
- ItemMagnetic phase diagram and correlation between metamagnetism and superconductivity in Ru0.9Sr2YCu2.1O7.9(Springer, 2013-06-01) Nigam, R; Kennedy, SJ; Pan, AV; Dou, SXThe magnetic superconductor Ru0.9Sr2YCu2.1O7.9 (Ru-1212Y) has been investigated using neutron diffraction under variable temperature and magnetic field. With the complementary information from magnetization measurements, we propose a magnetic phase diagram T-H for the Ru-1212 system. Uniaxial antiferromagnetic (AFM) order of 1.2 mu(B)/Ru atoms with moments parallel to the c-axis is found below the magnetic transition temperature at similar to 140 K in the absence of magnetic field. In addition, ferromagnetism (FM) in the ab-plane develops below similar to 120 K, but is suppressed at lower temperature by superconducting correlations. Externally applied magnetic fields cause Ru-moments to realign from the c-axis to the ab-plane, i.e. along the < 1, 1, 0 > direction, and induce ferromagnetism in the plane with similar to 1 mu(B) at 60 kOe. These observations of the weak ferromagnetism suppressed by superconductivity and the field-induced metamagnetic transition between AFM and FM demonstrate not only competing orders of superconductivity and magnetism, but also suggest a certain vortex dynamics contributing to these magnetic transitions. © 2013, Springer.
- 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.
- 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.
- ItemThe role of multilayering in the significant improvement of structural and superconducting properties in high-Tc films(Australian Institute of Physics, 2006-02-07) Pan, AV; Pysarenko, SV; Roussel, M; Dou, SX; Ionescu, MBy introducing multilayered structures to YBa2Cu3O7 (YBCO) films, significant improvement of superconducting and structural properties in the obtained multilayers has been obtained. A sandwich-like system with three main YBCO layers of ~300 nm thick and two additional NdBCO layers of about ~50 nm thick in between the YBCO layers exhibits much smoother surface compared to the YBCO films of the same thickness. It has critical current density (Jc) which is not only significantly larger (by a factor > 3) than that obtained in YBCO films with the same thickness (1 μm), but also larger than Jc in mono-layer YBCO films of any smaller thickness. The Jc enhancement is observed in both low field and high field regions, which attributed to a larger filling factor of the multilayer, better grain alignment and additional formation of dislocations at the interfaces between the layers.
- ItemVortex-glass phase transition and enhanced flux pinning in C4+-irradiated BaFe1.9Ni0.1As2 superconducting single crystals(IOP Publishing, 2013-08-13) Shabhazi, M; Wang, XL; Ghorbani, SR; Ionescu, M; Shcherbakova, OV; Wells, FS; Pan, AV; Dou, SX; Choi, KYWe report the effects of C4+-irradiation on the superconducting properties of BaFe1.9Ni0.1As2 single crystal. The BaFe1.9Ni0.1As2 single crystal before and after C4+-irradiation was characterized by magnetic, magneto-transport and magneto-optical techniques over a wide range of magnetic fields (0–13 T) and temperatures (2–200 K). We demonstrate that the C4+-irradiation significantly enhances the in-field critical current density (by a factor of up to 1.5 at 5 K) and induces enhanced flux jumping at 2 K, with only a small degradation (by 0.5 K) of the critical temperature, Tc. The vortex phase diagram describing the evolution of the vortex-glass transition temperature with magnetic field and the upper critical field has been resolved for the C4+-irradiated sample. For temperatures below Tc, the resistivity curves and the pinning potential were found to show good scaling, using a modified model for vortex-liquid resistivity. The vortex state is three dimensional at temperatures lower than a characteristic temperature. Good agreement between the thermally activated flux flow model, which is usually employed to account for the resistivity in the vortex-liquid region, and the modified vortex-liquid model, has been observed. © 2013 IOP Publishing