journal

Journal of Physics. Condensed Matter: An Institute of Physics Journal

journal
#1
P V Sreenivasa Reddy, V Kanchana, G Vaitheeswaran, Andrei V Ruban, N E Christensen
A detailed study on the ternary Zr-based intermetallic compound Zr2TiAl has been carried out using first-principles electronic structure calculations. From the total energy calculations, we find an antiferromagnetic L11-like (AFM) phase with alternating (1 1 1) spin-up and spin-down layers to be a stable phase among some others with magnetic moment on Ti being 1.22 [Formula: see text]. The calculated magnetic exchange interaction parameters of the Heisenberg Hamiltonian and subsequent Heisenberg Monte Carlo simulations confirm that this phase is the magnetic ground structure with Néel temperature between 30 and 100 K...
May 26, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
#2
Katlyn M Turner, Dylan R Rittman, Rachel A Heymach, Cameron L Tracy, Madison L Turner, Antonio F Fuentes, Wendy L Mao, Rodney C Ewing
Complex oxides with the pyrochlore (A2B2O7) and defect-fluorite ((A,B)4O7) structure-types undergo structural transformations under high-pressure. Rare-earth hafnates (A2Hf2O7) form the pyrochlore structure for A  =  La-Tb and the defect-fluorite structure for A  =  Dy-Lu. High-pressure transformations in A2Hf2O7 pyrochlore (A  =  Sm, Eu, Gd) and defect-fluorite (A  =  Dy, Y, Yb) were investigated up to ~50 GPa and characterized by in situ Raman spectroscopy and synchrotron x-ray diffraction (XRD)...
May 25, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
#3
Taras Leonidovych Petrenko, V Bryksa
At present nitrogen-vacancy (NV) complex in diamond is the most promising defect for application in the area of quantum computing. This provides a stimulus for extensive search of another defects in semiconductors with similar properties. Recently it was shown that N$_{C}$V$_{Si}$ defect complex in SiC is perspective for this goal as well. In the present work we perform comparative \textit{ab initio} studies of NV complexes in diamond and 3\textit{C}-SiC. We focus both on radiospectroscopic characterization of these defects and on calculation of equilibrium concentration of complexes in irradiated crystals...
May 25, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
#4
Galvin Khara, Samuel Murphy, Dorothy M Duffy
A coupled two-temperature, molecular dynamics methodology is used to simulate the structural evolution of bcc metals (Fe and W) and fcc metals (Cu and Ni) following irradiation by swift heavy ions. Electronic temperature dependent electronic specific heat capacities and electron phonon coupling strengths are used to capture the full effects of the variation in the electronic density of states. Tungsten is found to be significantly more resistant to damage than iron, due both to the higher melting temperature and the higher thermal conductivity...
May 25, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
#5
Xianqing Lin, Jun Ni
First-principles calculations have been performed to study the intrinsic spin Hall effect (SHE) and its behavior under vertical electric field in monoclinic transition metal dichalcogenide monolayers (1T$'$-MX$_2$ with M = Mo, W and X = S, Se, Te). We find that the pristine systems exhibit nonquantized intrinsic spin Hall conductivity (SHC) due to the unconserved spin around the direct band gaps though they have nontrivial band topology. The unconserved spin is attributed to the band crossings at Fermi levels for systems without SOC and the distinct composition of the band states around the crossings...
May 25, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
#6
Ritu Gupta, S K Dhar, A Thamizhavel, K P Rajeev, Z Hossain
We present results of our comprehensive studies on single crystalline LaPt2Si2. Pronounced anomaly in electrical resistivity and heat capacity confirms the bulk nature of superconductivity (SC) and charge density wave (CDW) transition in the single crystals. While the charge density wave transition temperature is lower, the superconducting transition temperature is higher in single crystal compared to the polycrystalline sample. This result confirms the competing nature of CDW and SC. Another important finding is the anomalous temperature dependence of upper critical field H C2(T)...
May 24, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
#7
H J Elmers, D Kutnyakhov, S V Chernov, K Medjanik, O Fedchenko, A Zaporozhchenko-Zymakova, M Ellguth, C Tusche, J Viefhaus, G Schönhense
Spin-momentum locking of surface states has attracted great interest in recent years due to envisioned technological applications in the field of spintronics. Normal metal surfaces like W(1 1 0) and Ir(1 1 1) show surface states with energy dispersions and spin-polarization textures, which are reminiscent of topologically non-trivial surface states. In order to understand this phenomenon the connection of bulk and surface states has to be explored. Using time-of-flight momentum microscopy with soft x-ray excitation, we present a comprehensive analysis of the bulk bands of W and Ir...
May 24, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
#8
Zhenhai Yu, Wei Wu, Pengchao Lu, Jinggeng Zhao, Jinguang Cheng, Qingyang Hu, Ye Yuan, Xin Li, Cuiying Pei, Fengjiao Chen, Zhipeng Yan, Shuai Yan, Ke Yang, Jian Sun, Jianlin Luo, Lin Wang
The influence of external pressure on the structural properties of manganese monophosphides (MnP) at room temperature has been studied using in situ angle dispersive synchrotron x-ray powder diffraction (AD-XRD) with a diamond anvil cell. The crystal structure of MnP is stable between 0 to 15 GPa. However, the compressibility of b-axis is much larger than those of a- and c-axes. From this result we suggested that the occurrence of superconductivity in MnP was induced by suppression of the long-range antiferromagnetically ordered state rather than a structural phase transition...
May 24, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
#9
Aniekan Ukpong
This paper presents the results of ab initio studies of the electronic spin manipulation, inversion, filtering and transport using a ferromagnetic multilayer heterostructure. Spin-polarized electronic structure calculations are performed based on van der Waals density functional theory to give unique insights to the generation, manipulation and transport of coherent spin conductance. By using an exact theory of the self-consistent ground state of the Fe-hBN/graphene multilayer as a model of the magnetic tunnel junction, this paper unravels the hidden asymmetries in the spin-resolved charge densities...
May 22, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
#10
Takashi Komesu, Duy Le, Iori Tanabe, Eike Schwier, Yohei Kojima, Mingtian Zheng, Kazuaki Taguchi, Miyamoto Koji, Taichi Okuda, Hideaki Iwasawa, Kenya Shimada, Talat Rahman, Peter Dowben
We have investigated the influence of metal adsorbates (sodium and cobalt) on the occupied and unoccupied electronic structure of MoS2(0001) and WSe2(0001), through a combination of both photoemission and inverse photoemission. The electronic structure is rigidly shifted in both the WSe2 and MoS2 systems, with either Na or Co adsorption, generally as predicted by accompanying density functional theory based calculations. Na adsorption is found to behave as an electron donor (n-type) in MoS2, while Co adsorption acts as an electron acceptor (p-type) in WSe2...
May 22, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
#11
Ruslan Salikhov, Ludwig Reichel, Benjamin Zingsem, Radu Abrudan, Alexander Edström, Danny Thonig, Jan Rusz, Olle Eriksson, Ludwig Schultz, Sebastian Fahler, Michael Farle, Ulf Wiedwald
Tetragonally strained interstitial Fe-Co-B alloys were synthesized as epitaxial films grown on a 20 nm thick Au0.55Cu0.45 buffer layer. Different ratios of the perpendicular to in-plane lattice constant c/a = 1.013, 1.034 and 1.02 were stabilized by adding interstitial boron with different concentrations 0, 4, and 10 at.%, respectively. Using ferromagnetic resonance (FMR) and x-ray magnetic circular dichroism (XMCD) we found that the total orbital magnetic moment significantly increases with increasing c/a ratio, indicating that reduced crystal symmetry and interstitial B leads to a noticeable enhancement of the effect of spin-orbit coupling (SOC) in the Fe-Co-B alloys...
May 22, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
#12
Sangita de Sarkar, Amit Agarwal, Krishnendu Sengupta
We study transport properties of a phosphorene monolayer in the presence of single and multiple potential barriers of height $U_0$ and width $d$, using both continuum and microscopic lattice models, and show that the nature of electron transport along its armchair edge ($x$ direction) is qualitatively different from its counterpart in both conventional two-dimensional electron gas with Schr\"odinger-like quasiparticles and graphene or surfaces of topological insulators hosting massless Dirac quasiparticles...
May 22, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
#13
S Thamban, U Arjun, M Padmanabhan, R Nath
We present the synthesis and a detailed investigation of structural and magnetic properties of metal-organic compound Cu2(IPA)2(DMF)(H2O) by means of x-ray diffraction, magnetization, and heat capacity measurements. Single crystals of the title compound were synthesized by judicious selection of organic ligand and employing a selective hydrothermal reaction route. It crystallizes in an orthorhombic structure with space group Cmca. The structural analysis revealed that two Cu(2+) ions are held together by the organic component (-O-C-O-) in a square paddle-wheel to form spin dimers which are aligned perpendicular to each other and are further coupled through organic ligands (isophthalic acid) forming two-dimensional layers...
May 18, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
#14
Jian Liu, Wen-Jie Hou, Cai Cheng, Hui-Xia Fu, Jia-Tao Sun, Sheng Meng
Intrinsic valley polarization can be obtained in VSe2 monolayers with broken inversion symmetry and time reversal symmetry. First-principles investigations reveal that the magnitude of the valley splitting in magnetic VSe2 induced by spin-orbit coupling reaches as high as 78.2 meV and can be linearly tuned by biaxial strain. Besides conventional polarized light, hole doping or illumination with light of proper frequency can offer effective routes to realize valley polarization. Moreover, spin-orbit coupling in monolayer VSe2 breaks not only the valley degeneracy but also the three-fold rotational symmetry in band structure...
May 18, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
#15
Charles Paillard, Raymond Walter, Surendra Singh, Brahim Dkhil, L Bellaiche
A toy model combining the angular magneto electric (AME) coupling Hamitonian (Mondal et al 2015 Phys. Rev. B 92 100402) with long-range magnetic dipolar interactions is used to investigate spin-torque phenomena in a magnetic spin valve. It is found that such model (1) gives rise to spin-torque expressions that are analogous in form to those of the common spin-transfer torques; but also (2) predicts additional spin-torque terms, which are generated by an electrical current oriented along unconventional, in-plane directions...
May 18, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
#16
Manotosh Chakravorty, A K Raychaudhuri, Tapati Sarkar, Mikael Svante Andersson
In this paper we report the observation of a proposed Bose-Einstein condensation (BEC) of magnons in a temperature range of around 15-20 K in nanostructured films of Gd with grain sizes that are much larger than the size range where superparamagentism is expected. The observation was carried out using magnetic as well as high precision resistivity and magnetoresistance (MR) measurements performed to low temperatures. We observe that the experimental observations depend crucially on one parameter, namely softening of the spin wave stiffness parameter D at BEC and the resistivity as well as MR can be related quantitatively to magnetic measurements through the temperature variation of the constant D in the vicinity of the transition...
May 18, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
#17
Toni Helm, Patrick Valdivia, Edith Bourret-Courchesne, James Analytis, Robert Birgeneau
We performed resistance measurements on Fe<sub><i>1+δ-x</i></sub>Cu<sub><i>x</i></sub>Te with <i>x</i><sub>EDX</sub> ≦ <it>0.06</it> in the presence of in-plane applied magnetic fields, revealing a resistance anisotropy that can be induced at a temperature far below the structural and magnetic zero-field transition temperatures. The observed resistance anisotropy strongly depends on the field orientation with respect to the crystallographic axes, as well as on the field-cooling (FC) history...
May 17, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
#18
Xiaoxia Guo, Kongshuang Zhao
We report here a dielectric study on cationic and anionic spherical polyelectrolyte brushes (SPBs) (consisting of a polystyrene (PS) core and poly (2-aminoethylmethacrylate hydrochloride (PAEMH) chains or poly (acrylic acid) (PAA) chains grafted onto the core) suspensions over a frequency range of 40 Hz to 110 MHz. The relaxation behavior of the suspensions shows significant changes in the brush layer properties when changing particles mass fraction or pH of system. After eliminating electrode polarization effect at low frequency, two definite relaxations related to the interfacial polarization, around 100 kHz and 10 MHz respectively, are observed...
May 17, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
#19
Peet Cremer, Marco Heinen, Andreas Menzel, Hartmut Lowen
Ferrogels consist of magnetic colloidal particles embedded in an elastic polymer matrix. As a consequence, their structural and rheological properties are governed by a competition between magnetic particle-particle interactions and mechanical matrix elasticity. Typically the particles are permanently fixed within the matrix, which makes them distinguishable by their positions. Over time, particle neighbors do not change due to the fixation by the matrix. Here we present a classical density functional approach for such ferrogels...
May 17, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
#20
We study the Kondo lattice Shastry-Sutherland model with additional Dzyaloshinskii-Moriya~(DM) interactions, exploring the possible magnetic phases in its multi-dimensional parameter space. Treating the local moments as classical spins and using a variational ansatz, we identify the parameter ranges over which various common magnetic orderings are potentially stabilized. Our results reveal that the competing interactions result in a heightened susceptibility towards a wide range of spin configurations including longitudinal ferromagnetic and antiferromagnetic order, coplanar flux configurations and most interestingly, multiple non-coplanar configurations including a novel canted flux state as the different Hamiltonian parameters like electron density, interaction strengths and degree of frustration are varied...
May 17, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
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