Physical Sciences and Mathematics Commons^™

Magnetic Transitions In Lafe13-X-Ycoysix Compounds, Jianli Wang, S J. Campbell, S J. Kennedy, P Shamba, R Zeng, S X. Dou, G H. Wu

Shi Xue Dou

The magnetic properties of a set of LaFe13−x−yCoySix compounds (x = 1.6 − 2.6; y = 0, y = 1.0) have been investigated using magnetic measurements, thermal expansion, 57Fe Mössbauer spectroscopy and high resolution neutron powder diffraction methods over the temperature range 10–300 K. The natures of the magnetic transitions in these LaFe13−x−yCoySix compounds have been determined. The Curie temperatures of LaFe13−xSix were found to increase with Si content from TC = 219(5) K for Si content x = 1.6 to TC = 250(5) K for x = 2.6. Substitution of Co for Fe in LaFe10.4Si2.6 resulted in a further …

Platinum Dendritic Nanoparticles With Magnetic Behavior, Wenxian Li, Ziqi Sun, Dongliang Tian, Ivan P. Nevirkovets, S X. Dou

Shi Xue Dou

Magnetic nanoparticles have attracted increasing attention for biomedical applications in magnetic resonance imaging, high frequency magnetic field hyperthermia therapies, and magnetic-field-gradient-targeted drug delivery. In this study, three-dimensional (3D) platinum nanostructures with large surface area that features magnetic behavior have been demonstrated. The well-developed 3D nanodendrites consist of plentiful interconnected nano-arms ∼4 nm in size. The magnetic behavior of the 3D dendritic Pt nanoparticles is contributed by the localization of surface electrons due to strongly bonded oxygen/Pluronic F127 and the local magnetic moment induced by oxygen vacancies on the neighboring Pt and O atoms. The magnetization of the nanoparticles exhibits a …

Magnetic Properties And Magnetocaloric Effect Of Ndmn2-Xcuxsi2 Compounds, M F. Md Din, Jianli Wang, M Avdeev, Q F. Gu, R Zeng, S J. Campbell, S J. Kennedy, S X. Dou

Shi Xue Dou

Structural and magnetic properties of NdMn2−x Cu xSi2 compounds (x = 0-1.0) have been investigated by high intensity x-ray and resolution neutron diffraction (3-450 K), specific heat, dc magnetization, and differential scanning calorimetry measurements. Substitution of Cu for Mn leads to an increase in the lattice parameter a but a decrease in c at room temperature. Two magnetic phase transitions have been found for NdMn2−x Cu xSi2 compounds with TN for the antiferromagnetic ordering of Mn-sublatttice and TC for the Nd-sublattice ferromagnetic ordering, respectively. TC increases significantly with increasing Cu content from 36 K at x = 0 to 100 …

A Comparative Study Of Magnetic Behaviors In Tbni2, Tbmn2 And Tbni2mn, Jianli Wang, M F. Md Din, Shane Kennedy, F Hong, Stewart J. Campbell, A J. Studer, G H. Wu, Zhenxiang Cheng, S X. Dou

Shi Xue Dou

All TbNi2, TbMn2, and TbNi2Mn compounds exhibit the cubic Laves phase with AB2-type structure in spite of the fact that the ratio of the Tb to transition-metal components in TbNi2Mn is 1:3. Rietveld refinement indicates that in TbNi2Mn the Mn atoms are distributed on both the A (8a) and B (16d) sites. The values of the lattice constants were measured to be a = 14.348 Å (space group F-43 m), 7.618 Å, and 7.158 Å (space group Fd-3 m) for TbNi2, TbMn2, and TbNi2Mn, respectively. The magnetic transition temperatures TC were found to be TC = 38 K and TC …

Tunable Magnetic Properties Of Transition Metal Doped Mos2, Antonis N. Andiotis, Madhu Menon

Physics and Astronomy Faculty Publications

We report a detailed investigation of the electronic and magnetic properties of the transition metal (TM) doped two-dimensional (2D) MoS₂ using ab initio calculations. The doping is achieved by substituting two or more Mo atoms by TM atoms of the 3d series. Additionally, the effect of codoping on the 2D MoS₂ by cation-cation and cation-anion pairs is also investigated. Our results demonstrate that the TM doping of 2D MoS₂ leads to a significant reduction of the energy gap and the appearance of magnetic features whose major characteristic is the ferromagnetic coupling of the TM dopants. The …

Magnetic Correlations And Pairing In The 1/5-Depleted Square Lattice Hubbard Model, Ehsan Khatami, Rajiv R.P. Singh, Warren E. Pickett, Richard T. Scalettar

Faculty Publications

We study the single-orbital Hubbard model on the 1/5-depleted square-lattice geometry, which arises in such diverse systems as the spin-gap magnetic insulator CaV4O9 and ordered-vacancy iron selenides, presenting new issues regarding the origin of both magnetic ordering and superconductivity in these materials. We find a rich phase diagram that includes a plaquette singlet phase, a dimer singlet phase, a Néel and a block-spin antiferromagnetic phase, and stripe phases. Quantum Monte Carlo simulations show that the dominant pairing correlations at half filling change character from d wave in the plaquette phase to extended s wave upon transition to the Néel phase. …

Recent Ideas On The Calculation Of Lepton Anomalous Magnetic Moments, Michael I. Eides

Physics and Astronomy Faculty Publications

We discuss the recent claim [G. Mishima, arXiv:1311.7109; M. Fael and M. Passera, arXiv:1402.1575 [Phys. Rev. D (to be published)]] about discovery of a nonperturbative quantum-electrodynamic contribution of order (α/π)⁵ to lepton anomalous magnetic moments. We explain why this nonperturbative correction does not exist.

Isotropic Oscillator Under A Magnetic And Spatially Varying Electric Field, David L. Frost Mr., Frank Hagelberg

Undergraduate Honors Theses

We investigate the energy levels of a particle confined in the isotropic oscillator potential with a magnetic and spatially varying electric field. Here we are able to exactly solve the Schrodinger equation, using matrix methods, for the first excited states. To this end we find that the spatial gradient of the electric field acts as a magnetic field in certain circumstances. Here we present the changes in the energy levels as functions of the electric field, and other parameters.

The Jahn–Teller Effect And Electron–Phonon Interaction In La0.25ca0.75mn1−Xcrxo3, H. Zhou, G. Li, H. Chen, R. Zheng, Xiaojuan Fan, X. Li

Xiaojuan Fan

The ultrasonic (longitudinal and transverse) velocities and the transport and magnetic properties of polycrystalline La0.25Ca0.75Mn1-xCrxO3 (x = 0, 0.03, 0.05, and 0.07) have been studied systematically. It was found that with increasing Cr content, the resistivity increases, the charge-ordering transition temperature TCO shifts to low temperature, and the magnetic moment of the system is strengthened. From the temperature dependence of the ultrasonic velocities, one can establish that the Jahn-Teller energy and phonon exchange constant decrease with increasing Cr content.

Geophysical Analysis And Modelling Of The S‹Mav Basin, Western Anatolia, Ceyhan Ertan Toker

Bulletin of the Mineral Research and Exploration

The various data processing techniques, to illuminate the parameters of the geological structure which are applied in gravity and magnetic potential field methods. Also edge detection procedures are in data processing techniques. In this study, 2D, 3D, inversion and asta technique is one of the new edge detection procedures were applied to clarify correlation between the Simav half graben’s deep position and geometry of the tectonic lineaments. The Asta is obtained using the tilt angle.

Enhancing Superconducting Properties Of Mgb2 Pellets By Addition Of Amorphous Magnetic Ni-Co-B Nanoparticles, Mislav Mustapic, Josip Horvat, Md Shahriar Hossain, Zeljko Skoko, S X. Dou

Josip Horvat

Amorphous magnetic Ni-Co-B nanoparticles with an average size of 5 nm were added to precursor powders of MgB2 superconductor. The preparation procedure for MgB2 pellets was optimized for obtaining the best critical current density (Jc) at elevated magnetic fields. Addition of Ni-Co-B decreases the Jc for heat treatment of precursor powders at 650 ° C. Heat treatments at 770 ° C and higher improve Jc at 20 and 5 K. This improvement occurs at both temperatures through the increase of the effective connectivity between MgB2 crystals. Vortex pinning was enhanced at 5 K, but not at 20 K. Ni-Co-B nanoparticles …

Magnetic Properties And Magnetocaloric Effect Of Ndmn2−Xtixsi2 Compounds, M F. Md Din, Jianli Wang, S J. Campbell, R Zeng, W D. Hutchison, M Avdeev, S J. Kennedy, S X. Dou

Shi Xue Dou

The structural and magnetic properties of the intermetallic compounds NdMn2−xTixSi2(x = 0, 0.1, 0.2, and 0.3) have been studied by x-ray and high resolution neutron powder diffraction, specific heat, dc magnetization, and differential scanning calorimetry measurements over the temperature range 3–450 K. The Curie temperature and Néel temperature of NdMn2Si2 decrease from TC = 36 K and TN = 380 K to TC = 14 K and TN = 360 K, respectively, on substitution of Ti (x = 0.3) for Mn. The magnetocaloric effect at the first order ferromagnetic phase transition at TC, has been investigated in detail. Under a …

Critical Phenomena And Estimation Of The Spontaneous Magnetization By A Magnetic Entropy Analysis In Mn0.96nb0.04coge Alloy, Jyotish C. Debnath, A M. Strydom, P Shamba, Jianli Wang, S X. Dou

Shi Xue Dou

Magnetic and magnetocaloric properties of the alloy Mn0.96Nb0.04CoGe have been investigated.

Enhancing Superconducting Properties Of Mgb2 Pellets By Addition Of Amorphous Magnetic Ni-Co-B Nanoparticles, Mislav Mustapic, Josip Horvat, Md Shahriar Hossain, Zeljko Skoko, S X. Dou

Shi Xue Dou

Amorphous magnetic Ni-Co-B nanoparticles with an average size of 5 nm were added to precursor powders of MgB2 superconductor. The preparation procedure for MgB2 pellets was optimized for obtaining the best critical current density (Jc) at elevated magnetic fields. Addition of Ni-Co-B decreases the Jc for heat treatment of precursor powders at 650 ° C. Heat treatments at 770 ° C and higher improve Jc at 20 and 5 K. This improvement occurs at both temperatures through the increase of the effective connectivity between MgB2 crystals. Vortex pinning was enhanced at 5 K, but not at 20 K. Ni-Co-B nanoparticles …

Magnetic Phase Transitions And Entropy Change In Layered Ndmn1.7cr0.3si2, M F. Md Din, Jianli Wang, S J. Campbell, A J. Studer, M Avdeev, S J. Kennedy, Q F. Gu, R Zeng, S X. Dou

Shi Xue Dou

A giant magnetocaloric effect has been observed around the Curie temperature, TC ∼ 42 K, in NdMn1.7Cr0.3Si2 with no discernible thermal and magnetic hysteresis losses. Below 400 K, three magnetic phase transitions take place around 380 K, 320 K and 42 K. Detailed high resolution synchrotron and neutron powder diffraction (10-400 K) confirmed the magnetic transitions and phases as follows: TN intra ∼ 380 K denotes the transition from paramagnetism to intralayer antiferromagnetism (AFl), TN inter ∼ 320 K represents the transition from the AFl structure to the canted antiferromagnetic spin structure (AFmc), while TC ∼ 42 K denotes the …

Magnetism And Magnetic Structures Of Prmn2ge2-Xsix, Jianli Wang, S J. Campbell, M Hofmann, S J. Kennedy, R Zeng, M Md Din, S X. Dou, A Arulraj, N Stusser

Shi Xue Dou

The structural and magnetic properties of seven PrMn2Ge2-xSix compounds with Si concentrations in the range x = 0.0-2.0 have been investigated by x-ray diffraction, magnetic (5- 350 K), differential scanning calorimetry (300-500 K) and neutron diffraction (3-480 K) measurements. Replacement of Ge by Si leads to a contraction of the unit cell and significant modifications to the magnetic states-a crossover from ferromagnetism at room temperature for Ge-rich compounds to antiferromagnetism for Si-rich compounds. The compositional dependence of the room temperature lattice parameters exhibits non-linear behaviour around x = 1.2, reflecting the presence of magnetovolume effects. Re-entrant ferromagnetism has been observed …

The Flux Pinning Mechanism, And Electrical And Magnetic Anisotropy In Fe1.04te0.6se0.4 Superconducting Single Crystal, Mahboobeh Shahbazi-Manshadi, Xiaolin Wang, S X. Dou, H Fang, C T. Lin

Shi Xue Dou

The temperature and magnetic field dependences of the magnetization and critical current density of Fe1.04Te0.6Se0.4 single crystals have been investigated, and the flux pinning mechanism has been analysed. The normalized pinning force (fp Fp/F p,max) vs. h(H/Hirr) curves, are scaled using the Dew-Hughes theory, f(h) ≈ hp(1 - h)q with p 1.35 and q 3.06. The angular dependence of the resistivity under different magnetic fields shows a dip-like structure, below the superconducting transition temperature. The anisotropic value of 2 was obtained using Ginzburg-Landau theory.

Band Structure, Magnetic, And Transport Properties Of Two Dimensional Compounds Sr2-Xgdxcoo4, Q W Yao, Xiaolin Wang, H Kimura, S X. Dou, Konstantin Konstantinov, Z X. Cheng, F Hong, H Zhao, H Qiu, Kiyoshi Ozawa

Shi Xue Dou

The layered perovskite compound Sr2-xGdxCoO 4 has not yet been subjected to detailed study so far. In this report, structures, transport, magnetic properties, and first principle calculations will be reported for the two dimensional compounds Sr 2-xGdxCoO4 (x 0.5, 0.75, 1, 1.25). Rietveld refinement revealed that these compounds are crystallized in K2NiF 4-type structures with space group I4/mmm. It was found that the lattice parameter c decreases as x increases. Through the Curies Weiss fitting of the temperature dependent magnetization, it was found that the Sr 1.25Gd0.75CoO4 sample exhibits a weak ferromagnetic to paramagnetic transition at about 62 K, with …

Magnetic Phase Diagram And Correlation Between Metamagnetism And Superconductivity In Ru0.9sr2ycu2.1o7.9, Rashmi Nigam, Shane J. Kennedy, Alexey V. Pan, S X. Dou

Shi Xue Dou

The 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 1.2μ B/Ru atoms with moments parallel to the c-axis is found below the magnetic transition temperature at ~140 K in the absence of magnetic field. In addition, ferromagnetism (FM) in the ab-plane develops below ~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. …

Neutron Diffraction Study Of Mnniga2 - Structural And Magnetic Behaviour, Jianli Wang, L Ma, M Hofmann, M Avdeev, S J. Kennedy, S J. Campbell, M F. Md Din, M Hoelzel, G H. Wu, S X. Dou

Shi Xue Dou

MnNiGa2 crystallizes in the L21 (Heusler) structure and has a ferromagnetic ordering temperature TC ∼ 192 K. Rietveld refinement of the neutron diffraction patterns indicates that the Ga atoms occupy the equivalent 8c position, while Mn and Ni share the 4a (0, 0, 0) and 4b (0.5, 0.5, 0.5) sites with a mixed occupancy of Mn and Ni atoms. It is found that that ∼83% of Mn and ∼17% Ni are located at the 4a site while ∼83% of Ni and ∼17% Mn occupy the 4b site. There is no evidence of a magneto-volume effect around TC. In agreement with …

Surface Functionalization And Bioconjugation Of Nanoparticles For Biomedical Applications, Longyan Chen

Electronic Thesis and Dissertation Repository

Colloidal inorganic nanoparticles (NPs) have been attracting considerable interest in biomedicine, from drug and gene delivery to imaging, sensing and diagnostics. It is essential to modify the surface of nanoparticles to have enhanced biocompatibility and functionality for the in vitro and in vivo applications, especially in delivering locally and recognizing biomolecules. Herein, the goal of this research work is to develop advanced NPs with well-tailored surface functionalities and/or bio-functionality for the applications in cell tracking and analytes detection.

In the first project, quantum dots incorporating with gelatin nanoparticles (QDs-GNPs) have been developed for bioimaging applications. Two different approaches have been …

Magnetic Correlations And Pairing In The 1/5-Depleted Square Lattice Hubbard Model, Ehsan Khatami, Rajiv R.P. Singh, Warren E. Pickett, Richard T. Scalettar

Ehsan Khatami

We study the single-orbital Hubbard model on the 1/5-depleted square-lattice geometry, which arises in such diverse systems as the spin-gap magnetic insulator CaV4O9 and ordered-vacancy iron selenides, presenting new issues regarding the origin of both magnetic ordering and superconductivity in these materials. We find a rich phase diagram that includes a plaquette singlet phase, a dimer singlet phase, a Néel and a block-spin antiferromagnetic phase, and stripe phases. Quantum Monte Carlo simulations show that the dominant pairing correlations at half filling change character from d wave in the plaquette phase to extended s wave upon transition to the Néel phase. …

Magnetic Properties And Magnetocaloric Effect In Layered Ndmn1.9ti0.1si2, M F. Md Din, Jianli Wang, Shane J. Kennedy, Stewart J. Campbell, S X. Dou

Australian Institute for Innovative Materials - Papers

The structural and magnetic properties of the NdMn_1.9Ti_0.1Si₂ compund have been studied by high-intensity x-ray and high-resolution neutron powder diffraction, specific heat, dc magnetization, and differential scanning calorimetry measurements over the temperature range of 3-450 K. The Curie temperature and Néel temperature of layered NdMn_1.9Ti_0.1Si₂ are indicated as T_C ~ 22 K and T_N ~ 374 K respectively. The first order magnetic transition from antiferromagnetic [AFil-type] to ferromagnetic [F(Nd)+Fmc] around T_C is found in layered NdMn_1.9Ti_0.1Si₂ and is …

Direct Evidence Of Ni Magnetic Moment In Tbni2mn-X-Ray Magnetic Circular Dichroism, D H. Yu, Meng-Jie Huang, Jianli Wang, Hui-Chia Su, Hong-Ji Lin, Chien-Te Chen, S J. Campbell

Australian Institute for Innovative Materials - Papers

We have investigated the individual magnetic moments of Ni, Mn and Tb atoms in the intermetallic compound TbNi2Mn in the Laves phase (magnetic phase transition temperature TC ∼131 K) by X-ray magnetic circular dichroism (XMCD) studies at 300 K, 80 K and 20 K. Analyses of the experimental results reveal that Ni atoms at 20 K in an applied magnetic field of 1 T carry an intrinsic magnetic moment of spin and orbital magnetic moment contributions 0.53±0.01 μB and 0.05±0.01 μB, respectively. These moment values are similar to those of the maximum saturated moment of Ni element. A very small …

Magnetic Properties And Magnetocaloric Effect In Layered Ndmn 1.9v0.1si2, M F. Md Din, Jianli Wang, R Zeng, Shane Kennedy, S J. Campbell, S X. Dou

Australian Institute for Innovative Materials - Papers

The structural and magnetic properties of the compounds NdMn2-xVxSi2 have been studied by x-ray and high resolution neutron powder diffraction, specific heat, dc magnetization, and differential scanning calorimetry measurements over the temperature range 3-450 K. The Curie temperature and Néel temperature of layered NdMn1.9V0.1Si2 are been indicate at TC ~ 24 K and TN ~ 376 K respectively. The giant magnetocaloric effect (GMCE) around TC is found in layered NdMn1.9V0.1Si2 associated with first order magnetic transition from antiferromagnetic [AFil-type] to ferromagnetic [F(Nd)+Fmc]. This behaviorhas been confirmed as contribution of the magnetostructural coupling by using neutron powder diffraction. The magnetic entropy …

Platinum Dendritic Nanoparticles With Magnetic Behavior, Wenxian Li, Ziqi Sun, Dongliang Tian, Ivan P. Nevirkovets, S X. Dou

Australian Institute for Innovative Materials - Papers

Magnetic nanoparticles have attracted increasing attention for biomedical applications in magnetic resonance imaging, high frequency magnetic field hyperthermia therapies, and magnetic-field-gradient-targeted drug delivery. In this study, three-dimensional (3D) platinum nanostructures with large surface area that features magnetic behavior have been demonstrated. The well-developed 3D nanodendrites consist of plentiful interconnected nano-arms ∼4 nm in size. The magnetic behavior of the 3D dendritic Pt nanoparticles is contributed by the localization of surface electrons due to strongly bonded oxygen/Pluronic F127 and the local magnetic moment induced by oxygen vacancies on the neighboring Pt and O atoms. The magnetization of the nanoparticles exhibits a …

Magnetic Properties And Magnetocaloric Effect Of Ndmn2-Xcuxsi2 Compounds, M F. Md Din, Jianli Wang, M Avdeev, Q F. Gu, R Zeng, S J. Campbell, S J. Kennedy, S X. Dou

Australian Institute for Innovative Materials - Papers

Structural and magnetic properties of NdMn2−x Cu xSi2 compounds (x = 0-1.0) have been investigated by high intensity x-ray and resolution neutron diffraction (3-450 K), specific heat, dc magnetization, and differential scanning calorimetry measurements. Substitution of Cu for Mn leads to an increase in the lattice parameter a but a decrease in c at room temperature. Two magnetic phase transitions have been found for NdMn2−x Cu xSi2 compounds with TN for the antiferromagnetic ordering of Mn-sublatttice and TC for the Nd-sublattice ferromagnetic ordering, respectively. TC increases significantly with increasing Cu content from 36 K at x = 0 to 100 …

Significant Tunability Of Thin Film Functionalities Enabled By Manipulating Magnetic And Structural Nano-Domains, Igor A. Golovchanskiy, Alexey V. Pan, Sergey A. Fedoseev, Michael Higgins

Australian Institute for Innovative Materials - Papers

The influence of laser frequency on the structure and physical properties of thin films grown by pulsed laser deposition has been studied. Different types of thin films, hard ferromagnetic FePt L10 and quasi-single crystal superconducting YBa2Cu3O7 (YBCO), have been used for demonstration of the effect. Significant structural modifications have been obtained for the films with similar thicknesses. These modifications are shown to dramatically control their corresponding properties, providing an instrumental ability for tuning the practical characteristics of the films by changing the laser frequency of their deposition. In particular, 20-fold increase of coercive field and modification of demagnetization mechanism are …

Spin Memristive Magnetic Tunnel Junctions With Coo-Zno Nano Composite Barrier, Qiang Li, Ting-Ting Shen, Yan-Ling Cao, Kun Zhang, Shi-Shen Yan, Yu-Feng Tian, Shi-Shou Kang, Ming-Wen Zhao, You-Yong Dai, Yan-Xue Chen, Guo-Lei Liu, Liang-Mo Mei, Xiaolin Wang, Peter Grunberg

Australian Institute for Innovative Materials - Papers

The spin memristive devices combining memristance and tunneling magnetoresistance have promising applications in multibit nonvolatile data storage and artificial neuronal computing. However, it is a great challenge for simultaneous realization of large memristance and magnetoresistance in one nanoscale junction, because it is very hard to find a proper spacer layer which not only serves as good insulating layer for tunneling magnetoresistance but also easily switches between high and low resistance states under electrical field. Here we firstly propose to use nanon composite barrier layers of CoO-ZnO to fabricate the spin memristive Co/CoO-ZnO/Co magnetic tunnel junctions. The bipolar resistance switching ratio …

Magnetic Phase Transitions And Entropy Change In Layered Ndmn1.7cr0.3si2, M F. Md Din, Jianli Wang, S J. Campbell, A J. Studer, M Avdeev, S J. Kennedy, Q F. Gu, R Zeng, S X. Dou

Australian Institute for Innovative Materials - Papers

A giant magnetocaloric effect has been observed around the Curie temperature, TC ∼ 42 K, in NdMn1.7Cr0.3Si2 with no discernible thermal and magnetic hysteresis losses. Below 400 K, three magnetic phase transitions take place around 380 K, 320 K and 42 K. Detailed high resolution synchrotron and neutron powder diffraction (10-400 K) confirmed the magnetic transitions and phases as follows: TN intra ∼ 380 K denotes the transition from paramagnetism to intralayer antiferromagnetism (AFl), TN inter ∼ 320 K represents the transition from the AFl structure to the canted antiferromagnetic spin structure (AFmc), while TC ∼ 42 K denotes the …