Digital Commons Network^™

Structure, Magnetic, And Thermal Properties Of Nd1-Xlaxcro3 (0 ≤ X ≤ 1.0), Yi Du, Zhenxiang Cheng, Xiaolin Wang, S X. Dou

Shi Xue Dou

Perovskite-type Nd1−xLaxCrO3(0 ≤ x ≤1.0) polycrystalline samples were synthesized using solid state reaction. Structural studies indicate that the lattice parameters, metal–oxygen bond lengths, and angles of Nd1−xLaxCrO3 strongly depend on the La content. Two magnetic transition temperatures, Cr3+ antiferromagnetic ordering temperature (TN) and the spin reorientation phase transition temperature (TSRPT), have been observed in the M-T curves. The increase in TN and decrease in TSRPT with increasing x value can be explained by the change in the magnetic interactions due to La doping. The heat capacity of Nd1−xLaxCrO3 measured from 2 to 300 K reveals that the lattice, electronic, and …

Explanation Of Magnetic Behavior In Ru-Based Superconducting Ferromagnets, Rashmi Nigam, Alexey V. Pan, S X. Dou

Shi Xue Dou

We have investigated RuSr2Eu1.5Ce2O10 (Ru-1222) and RuSr2EuCu2O8 (Ru-1212) samples by using x-ray diffraction, scanning electron microscopy, dc magnetization, ac susceptibility, and resistivity measurements. Based on the results obtained, we propose an explanation of the magnetic behaviour of the Ru-based systems. Our model is capable of describing controversial observations of multiple magnetic transitions on temperature dependent dc magnetization measurements as well as the reentrance of irreversibility in hysteresis ≤200K. The experimental results suggest that Ru-based samples always contain a small amount of at least one additional magnetic phase with its own magnetic behaviour which is similar yet distinct from the main …

Giant Magnetic Entropy Change In Colossal Magnetoresistance In La0.7ca0.3mno3 Material In Low Field, Jyotish Debnath, Rong Zeng, Jung Ho Kim, S X. Dou

Shi Xue Dou

The structural, magnetic, and magnetocaloric properties of the manganite La0.7Ca0.3MnO3 have been studied. Change in the giant magnetic entropy was observed without any noticeable magnetic hysteresis but with small thermal hysteresis losses. We observed a first order magnetic phase transition around 251 K. The magnetic entropy change observed in this work is estimated to be 5.27 J/kg K for field changes from 0 to 1.5 T based on magnetization measurements. This value is about twice as large as those for other perovskite manganites and is even larger than for Gd-based magnetic materials at low fields. In addition, the entropy change …

Magnetic Anisotropy In Doped And Undoped Lifepo4 Single Crystals, Dapeng Chen, Xiaolin Wang, Y S Hu, C T Lin, S. X. Dou, Rashmi Nigam

Shi Xue Dou

We report on the magnetic anisotropic properties of pure and Mg doped LiFePO4 single crystals grown by the traveling solvent floating zone technique. Our results reveal a considerable anisotropy in the susceptibilities along H‖a, H‖b, and H‖c for both crystals. LiFePO4 and Li0.99Mg0.01FePO4 crystals show antiferromagnetic long-range ordering below the Néel temperature of about 52 K, with the b axis being the magnetic easy axis. The effective moments have been determined to be 6.18μB and 6.07μB for the pure and the doped crystals, respectively. These values are higher than what is expected on the basis of the spin-only value of …

Kinetic Roughening Of Magnetic Flux Penetration In Mgb2 Thin Films, Andrea Lucarelli, Stephanie Hummert, Andrea Chaney, Gunter Lupke, Brian Moeckly, Yue Zhao, S X. Dou

Shi Xue Dou

Time-resolved magneto-optical studies are performed on MgB2 thin film samples grown by in situ pulsed laser deposition and in situ reactive deposition technique. The latter reveal dendritic avalanche-free flux penetration. The kinetic roughening of magnetic flux penetration is studied for applied ac current. Dynamic scaling laws determined for both static field and ac current are consistent with the directed percolation depinning model, placing the vortex dynamics in MgB2 in the same universality class as YBCO and Nb.

Magnetic Glassy Behaviour In Ferroelectric Relaxor Type Solid Solutions: Magnetelectric Relaxor, Zhenxiang Cheng, Xiaolin Wang, Gustavo A. Alvarez, S. X. Dou, Shujun Zhang, Thomas R. Shrout

Shi Xue Dou

Perovskite solid solution ceramics with compositions of 0.9Pb(Fe0.5Nb0.5)O3–0.1PbTiO3, 0.6Pb(Ni1/3Nb2/3)O3–0.4PbTiO3, and 0.6Pb(Co1/3Nb2/3)O3–0.4PbTiO3 were synthesized by the traditional solid state reaction method. Ferroelectric measurements revealed that these samples have well saturated polarization-electrical field loops. Dielectric measurements showed that abnormal dielectric peaks at their Curie temperature were frequency dependent. Both characteristics indicate that these samples are relaxor type ferroelectric materials. Field cooled and zero field cooled magnetization measurements revealed that the 0.6Pb(Ni1/3Nb2/3)O3–0.4PbTiO3 and 0.6Pb(Co1/3Nb2/3)O3–0.4PbTiO3 samples are paramagnetic down to 5 K, while the 0.9Pb(Fe0.5Nb0.5)O3–0.1PbTiO3 sample shows an antiferromagnetic-like ordering starting from around 40 K. Furthermore, a weak ferromagnetism is observed in the 0.9Pb(Fe0.5Nb0.5)O3–0.1PbTiO3 …

Band Structures, Magnetic Properties, And Enhanced Magnetoresistance In The High Pressure Phase Of Gd And Y Doped Two-Dimensional Perovskite Sr2coo4 Compounds, Xiaolin Wang, E Takayama-Muromachi, S X. Dou, Zhenxiang Cheng

Shi Xue Dou

The authors present their studies on the band structures and on the magnetic and magnetotransport properties of the high pressure phase of Sr2-xRExCoO4 [rare earth (RE)=Gd and Y, x=0.1-0.5] compounds which were synthesized by a high pressure and high temperature technique. The authors found that as x increases, the magnetoresistance {(PH-P0)/p0} increases up to -17% at 5 K and 7 T, which is 2.5 times higher than that for undoped Sr2CoO4, although the ferromagnetic transition drops from 255 to 200 K for the Gd doping with x=0.3. The saturation moments at low temperature are significantly enhanced for the Gd doped …

Magnetic And Transport Properties Of Transition Metal Doped Polycrystalline In2o3, Germanas Peleckis, Xiaolin Wang, S X. Dou

Shi Xue Dou

Synthesis and characterization of transition metal (TM)-doped In 2O3 oxide is reported. Most of the samples were found to be paramagnetic, and only Ye and Cr co-doped sample showed as light trace of ferromagnetism at 300 K with saturation magnetization M s = 0.35 emug/g. Measured transport properties revealed significant differences in transport among the samples. The absolute value of electrical resistivity for the In1.8Fe0.1Mn0.1O3 sample at 300 K was rho= 9.4 x 103 Omega middot cm, while In1.8Fe0.1Cr0.1O3 had rho = 62 Omega middot cm at the same temperature. Furthermore, magnetoresistance (MR) studies of In1.8Fe0.1Cr0.1O3 showed that the sign …

Specific Heat And Magnetic Relaxation Analysis Of Mgb2 Bulk Samples With And Without Additives, C. Senatore, P. Lezza, R. Lortz, Olga V. Shcherbakova, Wai Kong Yeoh, S. X. Dou, R. Flukiger

Shi Xue Dou

The effects of SiC and Carbon doping on the superconducting properties of MgB2 polycrystalline samples have been analysed by means of specific heat and magnetic relaxation measurements. It is known that the addition of nanometric powders of SiC and C leads to the enhancement of Birr and Jc. However, the underlying physical mechanism is not completely understood. Magnetic relaxation measurements did not show detectable effects of both the additions on the pinning properties of MgB2. It follows that doping acts mainly introducing disorder into the superconductor and thus raising Bc2. In the case of MgB1.9C0.1, specific heat measurements show that …

Abnormal Magnetic Behaviors And Large Magnetocaloric Effect In Mnps3 Nanoparticles, R Zeng, S Q. Wang, G D. Du, Jianli Wang, J C. Debnath, Precious Shamba, Z Y. Fang, S. X. Dou

Shi Xue Dou

A nanostructured honeycomb lattice consisting of MnPS3 nanoparticles synthesized via the ion-exchange technique was found to have restacked molecular layers stabilized by H2O insertion between the layers. Susceptibility (χ) and heat capacity measurements showed the absence of long range magnetic ordering, at least down to 2 K. However, the χ data showed that the system possesses a high effective Curie temperature, suggesting that the system is in a high spin lattice disordered state. Evaluation of the magnetocaloric effect indicates that the system has a large reversible magnetic-entropy change (−ΔSm) of 6.8 and 12.8 J/kg K and an adiabatic temperature change …

Josephson-Vortex Flow Resistance In Bi2sr2ca2cu3oy Single Crystals And Its Possible Application In The Manipulation Of Spin And Charge Textures In Diluted Magnetic Semiconductors, Xiaolin Wang, C T Lin, B Liang, S Yu, S Ooi, K Hirata, S Y Ding, Dongqi Shi, S X. Dou, Zhi W. Lin, Jian G. Zhu

Shi Xue Dou

In this work, the flow of the Josephson vortices (JVs) has been studied for the highly anisotropic Bi2Sr2Ca2Cu3Oy (Bi2223) single crystals. A giant flow of JVs or giant positive magnetoresistance (MR) of over 500%-2000% was obtained in fields of 0.1-5 T and remained almost constant over a wide temperature range from 110 down to 4 K, in contrast to superconducting vortices (SVs), which only produced MR in the vicinity of Tc. The flow of the JVs is expected to be much faster than that of SVs. It is proposed that the Josephson vortices could be used to manipulate the spin …

Magnetic Anisotropy Of Naxcoo2 Single Crystals, Dapeng Chen, Xiaolin Wang, C T Lin, S X. Dou

Shi Xue Dou

We report the magnetic properties of single crystals of NaxCoO2 (x=0.42, 0.82, and 0.87). The magnetic susceptibility measurements revealed considerable anisotropy along H parallel to ab and H parallel to c for the as-grown single crystals. It was found that an antiferromagnetic transition with a Neel temperature T-N=21 K occurred for the x=0.82 sample, and there was a paramagnetic phase for the x=0.87 sample over a wide temperature range from 2 to 300 K, but the sample with x=0.42 shows a monotonic increase of chi with increasing temperature above similar to 100 K. In addition, the x=0.82 sample has the …

Magnetic And Ferroelectric Properties Of Multiferroic Bi2nimno6 Nanoparticles, Yi Du, Zhenxiang Cheng, Xiaolin Wang, Peng Liu, S. X. Dou

Shi Xue Dou

Multiferroic Bi2NiMnO6 nanoparticles were synthesized by a simple electrospray method. Bi2NiMnO6 nanoparticles crystallize in the monoclinic structure with space group C121. The particles show a uniform spherical shape with a diameter of 100 nm to 300 nm. The ferromagnetic transition of Bi2NiMnO6 is confirmed at 122 K. The room temperature ferroelectricity of the Bi2NiMnO6 nanoparticles is verified by Kelvin probe force microscopy.

Magnetic Properties And Magnetocaloric Effect Of (Mn1-Xnix)3sn2(X=0-0.5) Compounds, Rong Zeng, Lin Lu, Jung Ho Kim, Dongqi Shi, Hua-Kun Liu, S. X. Dou, Jianli Wang, Stewart J. Campbell, Zhaoxiang Wang, Y Li, Wenxian Li, M Y. Zhu, Chuanqi Feng

Shi Xue Dou

The effects of Ni substitution on the magnetic properties and magnetocaloric effect (MCE) of (Mn1−xNix)3Sn2 compounds (x = 0–0.5) have been investigated by x-ray diffraction and magnetization measurements. It was found that Ni substitution decreases the crystal cell volume and the magnetic transition temperatures compared with pure Mn3Sn2. The MCE for all samples has been calculated from the magnetization data in terms of the isothermal magnetic entropy change ΔSM. The maximum values of ΔSMmax at the magnetic phase transition temperatures resulting from a change in magnetic field of ΔH = 5 T were found to be 28.2 mJ/cm3 K for …

Critical Magnetic Transition In Tbni2mn-Magnetization And Mossbauer Spectroscopy, Jianli Wang, S J. Campbell, S J. Kennedy, Rong Zeng, S. X. Dou, Guangheng Wu

Shi Xue Dou

The structural and magnetic properties of the TbNi2Mnx series (0.9 ≤ x ≤ 1.10) have been investigated using x-ray diffraction, field- and temperature-dependent ac magnetic susceptibility,DC magnetization (5-340 K; 0-5 T) and 57Fe Mössbauer spectroscopy (5-300 K). TbNi2Mnx crystallize in the MgCu2-type structure (space group Fd-3m). The additional contributions to the magnetic energy terms from transition metal-transition metal interactions (T-T) and rare earthtransition metal interactions (R-T) in RNi2Mn contribute to their increased magnetic ordering temperatures compared with RNi2 and RMn2. Both the lattice constant a and the Curie temperature TC exhibit maximal values at the x=1 composition indicating strong magnetostructural …

Flux Pinning Of Stress Induced Magnetic Inhomogeneity In The Bilayers Of Yba2cu3o7-Δ/La0.67sr0.33mno3-Δ, S X. Dou, Rong Zeng, Y M. Lu, L Peng, B Gao, Z Y. Liu, F Fan, C B. Cai, C Z. Chen

Shi Xue Dou

Elaborately designed bilayers consisting of epitaxial YBa2Cu3O7-δ (YBCO) and La0.67Sr0.33MnO3-δ (LSMO) films were fabricated by pulsed laser deposition with respect to the investigation into magnetic-dependent vortex pinning effect. The improvement in the critical current density and a pronounced upward shift in the superconducting irreversibility line based on magnetotransport measurements are observed when compared to the pure YBCO film, suggesting the enhancement in flux pinning in the studied bilayer. It is believed that the improved flux pinning for YBCO arises from the magnetic inhomogeneity of the underlying LSMO. Magnetization measurements show a nonuniform magnetic state in the LSMO film, most probably …

Magnetic Propulsion Of A Spiral-Type Endoscopic Microrobot In A Real Small Intestine, Hao Zhou, Gursel Alici, Trung Duc Than, Weihua Li, Sylvain Martel

Gursel Alici

This paper reports on the magnetic propulsion of a spiral-type endoscopic mircorobot in a real small intestine. Magnetic modeling was carried out to design and commission an external electromagnetic system, which wirelessly provides power to the robotic agent. The capsules with different spiral structures were magnetically propelled inside a segment of porcine small intestine. From the results, it is shown that the propulsive velocities of the tested capsules are in the range of 2.5 ~ 35 mm/s when rotating frequencies varying between 1 ~ 5 Hz are applied. Among all the capsules prepared for this study, the capsule No. 5, …

Magnetic Propulsion Of A Spiral-Type Endoscopic Microrobot In A Real Small Intestine, Hao Zhou, Gursel Alici, Trung Duc Than, Weihua Li, Sylvain Martel

Professor Weihua Li

This paper reports on the magnetic propulsion of a spiral-type endoscopic mircorobot in a real small intestine. Magnetic modeling was carried out to design and commission an external electromagnetic system, which wirelessly provides power to the robotic agent. The capsules with different spiral structures were magnetically propelled inside a segment of porcine small intestine. From the results, it is shown that the propulsive velocities of the tested capsules are in the range of 2.5 ~ 35 mm/s when rotating frequencies varying between 1 ~ 5 Hz are applied. Among all the capsules prepared for this study, the capsule No. 5, …

Power System Applications Of Superconducting Magnetic Energy Storage Systems, X D. Xue, Eric Kw Cheng, Danny Sutanto

Professor Darmawan Sutanto

This study overviewed current researches on power system applications of SMES systems. Some key schematic diagrams of applications were given, too. Furthermore, the authors tried to present a few valuable suggestions for future studies of SMES applications to power systems.

Effect Of A Static Magnetic Field On Nanodosimetric Quantities In A Dna Volume, Peter Lazarakis, Marion U. Bug, Elisabetta Gargioni, Susanna Guatelli, Sabastien Incerti, Hans Rabus, Anatoly B. Rosenfeld

Susanna Guatelli

Abstract Purpose: With the advent of magnetic resonance imaging (MRI)-guided radiation therapy it is becoming increasingly important to consider the potential influence of a magnetic field on ionising radiation. This paper aims to study the effect of a magnetic field on the track structure of radiation to determine if the biological effectiveness may be altered. Methods: Using the Geant4-DNA (GEometry ANd Tracking 4) Monte Carlo simulation toolkit, nanodosimetric track structure parameters were calculated for electrons, protons and alpha particles moving in transverse magnetic fields up to 10 Tesla. Applying the model proposed by Garty et al., the track structure parameters …

Experimental Investigation Of The Vibration Characteristics Of A Magnetorheological Elastomer Sandwich Beam Under Non-Homogeneous Small Magnetic Fields, Guoliang Hu, Miao Guo, Weihua Li, Haiping Du, Gursel Alici

Dr Haiping Du

In this study, a magnetorheological elastomer (MRE) was manufactured and tested, and a MRE sandwich beam was also fabricated from a MRE between two thin aluminum layers. An experimental test rig was set up to investigate the vibration response of the MRE sandwich beam under a non-homogeneous magnetic field. The experimental results show that the first natural frequency of the MRE sandwich beam decreased as the magnetic field applied to the beam was moved from the clamped end of the beam to the free end of the beam. It is also noted that the MRE sandwich beam had the capability …

Experimental Investigation Of The Vibration Characteristics Of A Magnetorheological Elastomer Sandwich Beam Under Non-Homogeneous Small Magnetic Fields, Guoliang Hu, Miao Guo, Weihua Li, Haiping Du, Gursel Alici

Gursel Alici

In this study, a magnetorheological elastomer (MRE) was manufactured and tested, and a MRE sandwich beam was also fabricated from a MRE between two thin aluminum layers. An experimental test rig was set up to investigate the vibration response of the MRE sandwich beam under a non-homogeneous magnetic field. The experimental results show that the first natural frequency of the MRE sandwich beam decreased as the magnetic field applied to the beam was moved from the clamped end of the beam to the free end of the beam. It is also noted that the MRE sandwich beam had the capability …

Superspin Glass Behaviour Of Interacting Ferromagnetic Nanoparticles In Discontinuous Magnetic Multilayers, Christian Binek

Christian Binek

Discontinuous magnetic multilayers [Co80Fe20(t)/Al2O3(3nm)]10 with t = 0.9 and 1.0nm are studied by SQUID magnetometry and ac susceptibility. Owing to dipolar interaction the superparamagnetic cluster systems undergo collective glass-like freezing upon cooling. While both samples exhibit very similar glass temperatures Tg » 45 K and critical exponents zn » 10 and g » 1.4 as obtained from the temperature dependencies of the relaxation time, t, and the nonlinear susceptibility, c3, dynamical scaling reveals different critical exponents, b(0.9nm) »1.0 and b(1.0nm) » 0.6, respectively.

Light Diffraction By Field-Induced Non-Periodic Magnetic Domain Structures In Fecl2, Christian Binek

Christian Binek

The magnetic-field-induced mixed phase of the meta magnet FeCl2 gives rise to reduced transmittivity of circularly polarized light. Within the framework of the diffraction theory of thin random magnetic phase gratings and the assumption of field-dependent refractive indices of the antiferromagnetic domains the field dependence of the transmission is perfectly modeled.

Random-Field Critical And Spin-Flop Behavior Of The Anisotropic Heisenberg Antiferromagnet Fe0.9mg0.1br2 In Axial Magnetic Fields, Christian Binek

Christian Binek

Faraday optical measurements on the dilute hexagonal antiferromagnet Fe0.85Mg0.15Br2 in an external axial field reveal a spin-flop phase line ending at a multicritical point (Tm=8.1 K, Hm=1050 kA m-1) and crossover from random-exchange to random-field Ising criticality with an exponent Phi =1.40+or-0.04 in the vicinity of TN=11.1 K. Cusp-like behaviour of the specific heat at TN is discussed in view of recent Monte Carlo results.

Fiber Metamaterials With Negative Magnetic Permeability In The Terahertz, Anna Wang, Alessandro Tuniz, Peter Hunt, Elise Pogson, R A. Lewis, Avi Bendavid, Simon Fleming, Boris Kuhlmey, Maryanne Large

Roger A. Lewis

We present a novel method for producing metamaterials with a terahertz magnetic response via fiber drawing, which can be inexpensively scaled up to mass production. We draw a centimeter preform to fiber, spool it, and partially sputter it with metal to produce extended slotted resonators. We characterize metamaterial fiber arrays with different orientations via terahertz time domain spectroscopy, observing distinct magnetic resonances between 0.3 and 0.4 THz, in excellent agreement with simulations. Numerical parameters retrieval techniques confirm that such metamaterials possess negative magnetic permeability. Combined with fiber-based negative permittivity materials, this will enable the development of the first woven negative …

Magneto-Radiotherapy: Effect Of Magnetic Field On Dose Distribution And Rbe, Heidi Nettelbeck, Anatoly B. Rosenfeld, George J. Takacs, Michael L. Lerch

George Takacs

Magneto-radiotherapy is the application of magnetic fields during radiotherapy procedures. It aims to improve the quality of cancer treatment by altering the dose deposition of charged particles in the tissue volume being targeted. Our research has focused on applying the concept of magneto-radiotherapy to conventional linac treatment and MRT (Microbeam Radiation Therapy) oncology modalities.

Magnetic And Transport Properties Of The V2– Vi3 Diluted Magnetic Semiconductor Sb2_Xmnxte3, Jeffrey Dyck, P. Svanda, P. Lostak, J. Horak, W. Chen, C. Uher

Jeffrey Dyck

We have measured electrical and magnetic properties of single crystals of Sb2_xMnxTe3 with x =0 – 0.045 at temperatures of 2 K to 300 K. Hall effect measurements indicate that each manganese atom donates approximately one hole to the valence band. The magnetic susceptibility is paramagnetic down to 2 K, and both Curie–Weiss and Brillouin analyses show that manganese substitutes for Sb and takes the Mn2+ state with S=5/2. Contrary to the case of III–V host matrices, manganese does not stimulate ferromagnetic order in the family of bulk layered V2– VI3 diluted magnetic semiconductors, at least in the range of …

Methyl Ester Carboxylates: A Nuclear Magnetic Resonance Study, William Macknight

William MacKnight