118 research outputs found
Origin of time reversal symmetry breaking in Y(1-y)Ca(y)Ba(2)Cu(3)O(7-x)
We have studied the Zero Bias Conductance Peak (ZBCP) of the tunneling
conductance measured on (1,1,0) oriented Y(1-y)Ca(y)Ba(2)Cu(3)O(7-x) thin films
as a function of doping and of magnetic field. A spontaneous (zero field) split
of the ZBCP was observed only in overdoped samples (either by O or by Ca). The
magnitude of this split was found to be linear in doping. All samples exhibited
a magnetic field splitting, also strongly doping dependent. The field
susceptibility chi=d(delta)/dH diverges at the point at which spontaneous ZBCP
splitting occurs, its inverse value, chi^(-1), following a linear doping
dependence on both the underdoped and overdoped sides. We discuss these results
in terms of recent theoretical models of Time Reversal Symmetry Breaking
(TRSB).Comment: 5 figure
Low Temperature Neutron Diffraction Study of MnTe
Investigation of transport and magnetic properties of MnTe at low
temperatures sInvestigation of transport and magnetic properties of MnTe at low
temperatures showed anomalies like negative coefficient of resistance below
100K and a sharp rise in susceptibility at around 83K similar to a
ferromagnetic transition. Low temperature powder neutron diffraction
experiments were therefore carried out to understand the underlying phenomena
responsible for such anomalous behavior. Our study indicates that the rise in
susceptibility at low temperatures is due to strengthening of ferromagnetic
interaction within the plane over the inter plane antiferromagnetic
interactions.Comment: Appearing in J. Magn. Magn. Mate
Anisotropy of the Optimally-Doped Iron Pnictide Superconductor Ba(Fe0.926Co0.074)2As2
Anisotropies of electrical resistivity, upper critical field, London
penetration depth and critical currents have been measured in single crystals
of the optimally doped iron pnictide superconductor
Ba(FeCo)As, =0.074 and 23 K. The normal state
resistivity anisotropy was obtained by employing both the Montgomery technique
and direct measurements on samples cut along principal crystallographic
directions. The ratio is about 41 just
above and becomes half of that at room temperature. The anisotropy of the
upper critical field, , as determined from
specific heat measurements close to , is in the range of 2.1 to 2.6,
depending on the criterion used. A comparable low anisotropy of the London
penetration depth, , was recorded
from TDR measurements and found to persist deep into the superconducting state.
An anisotropy of comparable magnitude was also found in the critical currents,
, as determined from both direct transport
measurements (1.5) and from the analysis of the magnetization data
(3). Overall, our results show that iron pnictide superconductors
manifest anisotropies consistent with essentially three-dimensional
intermetallic compound and bear little resemblance to cuprates
SodiumâDoped Tin Sulfide Single Crystal: A Nontoxic EarthâAbundant Material with High Thermoelectric Performance
Leadâfree tin sulfide (SnS), with an analogous structure to SnSe, has attracted increasing attention because of its theoretically predicted high thermoelectric performance. In practice, however, polycrystalline SnS performs rather poorly as a result of its low power factor. In this work, bulk sodium (Na)âdoped SnS single crystals are synthesized using a modified Bridgman method and a detailed transport evaluation is conducted. The highest zT value of â1.1 is reached at 870 K in a 2 at% Naâdoped SnS single crystal along the bâaxis direction, in which high power factors (2.0 mW mâ1 Kâ2 at room temperature) are realized. These high power factors are attributed to the high mobility associated with the single crystalline nature of the samples as well as to the enhanced carrier concentration achieved through Na doping. An effective single parabolic band model coupled with firstâprinciples calculations is used to provide theoretical insight into the electronic transport properties. This work demonstrates that SnSâbased single crystals composed of earthâabundant, lowâcost, and nontoxic chemical elements can exhibit high thermoelectric performance and thus hold potential for application in the area of waste heat recovery.Large size Sn1âxNaxS single crystals were firstly obtained using a modified Bridgman method. The multiple band feature along with the single crystalline nature favors a large power factor, leading to the highest dimensionless figure of merit (zT) of ~1.1 at 870 K for 2 at% Naâdoped SnS single crystal along the bâaxis, which is one of the best results for thermoelectric sulfides to date.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/145294/1/aenm201800087_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/145294/2/aenm201800087-sup-0001-S1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/145294/3/aenm201800087.pd
Preliminary dragonfly (Odonata) species list from the Pampa biome in Rio Grande do Sul, Brazil, with ecological notes for 19 new records for the State
The genus podocarpus in the Netherlands Indies
When delimiting the area to be dealt with in this paper, it appeared, on the one hand, desirable to include some adjacent regions, such as the Malay Peninsula, North Borneo, Eastern New Guinea, the Bismarck Archipelago, and the Solomon Islands; on the other hand the war made it impossible to obtain herbarium materials from several Herbaria in Europe and the Tropics, and to elaborate the genus Podocarpus for the whole of Malaysia. Especially the Philippine Islands could not be taken into consideration, but the few materials I had the opportunity of examining have been included. I believe this treatment of the genus Podocarpus is rather complete for the Netherlands Indies proper.
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