Influence of negative-U centers on the temperature dependence of the carrier concentration in the normal HTSC phase

2007 ◽  
Vol 105 (4) ◽  
pp. 788-792 ◽  
Author(s):  
K. D. Tsendin ◽  
I. A. Barygin ◽  
A. I. Kapustin ◽  
B. P. Popov
Keyword(s):  
Temperature Dependence ◽  
Carrier Concentration

scholarly journals Investigation of the electron and thermal transport in rare-earth nitrides

2021 ◽  
Author(s):  
◽  
Tanmay Maity
Keyword(s):  
Transition Temperature ◽  
Temperature Dependence ◽  
Hall Effect ◽  
Carrier Concentration ◽  
Vacancy Concentration ◽  
Nitrogen Vacancy ◽  
Band Structure Calculation ◽  
Strong Temperature Dependence ◽  
Ferromagnetic Transition ◽  
Gadolinium Nitride

<p>Gadolinium nitride (GdN) and samarium nitride (SmN) have been widely studied to understand their ferromagnetic ordering and electronic structure, and for their promise in spintronics applications. This thesis presents experimental magnetotransport studies of GdN and SmN films in which experimental results have been compared with the existing band structure calculation. Three GdN films have been prepared in different conditions, among them two films are epitaxial quality and one film is polycrystalline in nature, and two films of SmN were also studied. Their magnetic properties were probed by SQUID magnetometry and they are found to be ferromagnetic. The transition temperature differs from sample to sample and this behaviour has been attributed to the presence of magnetic polarons that nucleate around nitrogen vacancies and give rise to an inhomogeneous ferromagnetic state.  The charge transport results have been discussed for all GdN and SmN films. A full set of charge/heat transport results are obtained on only one epitaxial GdN. The difference of resistivity among these samples is noticeable. The Hall effect results show the presence of different carrier concentration with at most only weak temperature dependence. We also have noticed the presence of anomalous Hall effect in the paramagnetic region for a lower-concentration epitaxial GdN.  The thermopower in both GdN and SmN was measured to provide further insight into the material’s electronic properties. In this thesis we present the first experimental investigation of the thermopower of epitaxial gadolinium nitride and samarium nitride films, measured using an experimental set-up designed for measuring the temperature dependent thermopower of thin films. Our result shows a negative thermopower for both GdN and SmN films and simple, though strong temperature dependence. At low temperatures we observe a peak near the ferromagnetic transition temperature in GdN. The results are interpreted in terms of the diffusion thermopower.  Overall the results suggest that the nitrogen vacancy concentration controls the carrier concentration and plays a significant role towards the transport properties. We conclude that all films are either heavily, moderately or weakly doped semiconductors with a metallic characteristic.</p>

c-Axis Resistivity Due to Transport of Fermionic Pairs in the Cuprates

1998 ◽  
Vol 12 (06n07) ◽  
pp. 225-230
Author(s):  
Manas Sardar
Keyword(s):  
Electron Transport ◽  
Fermi Surface ◽  
Temperature Dependence ◽  
Carrier Concentration ◽  
Density Of States ◽  
Low Temperatures ◽  
Single Electron ◽  
Acoustic Phonons ◽  
Single Electron Transport

With the assumption of complete incoherence of single electron transport along the c-axis, it is argued that it takes place by coherent hopping of singlet pairs that are fermionic in character. This will lead to a correction to the 1/Tc-axis resistivity calculated by Anderson et al.6 The c-axis resistivity coming from this extra channel of transport is shown to have the same temperature dependence as the inplane resistivity (linear in T) and mildly sensitive to the inplane carrier concentration through the modification of the density of states at the fermi surface. It is argued that the resistivity due to transport in this extra channel will be very sensitive to the c-axis disorder and show an upturn at low temperatures due to c-axis disorder and scattering by acoustic phonons.

Critical temperature dependence of YBa2Cu3Oy and Y1−xCaxBa2Cu3Oy on carrier concentration

1993 ◽  
Vol 206 (3-4) ◽  
pp. 291-296 ◽  
Author(s):  
Y. Sun ◽  
G. Strasser ◽  
E. Gornik ◽  
W. Seidenbusch ◽  
W. Rauch
Keyword(s):  
Critical Temperature ◽  
Temperature Dependence ◽  
Carrier Concentration

Temperature Dependence of Inversion Layer Carrier Concentration and Hall Mobility in 4H-SiC MOSFETs

2012 ◽  
Vol 717-720 ◽  
pp. 713-716 ◽  
Author(s):  
Sarit Dhar ◽  
Ayayi Claude Ahyi ◽  
John R. Williams ◽  
Sei Hyung Ryu ◽  
Anant K. Agarwal
Keyword(s):  
Temperature Dependence ◽  
Carrier Concentration ◽  
Hall Mobility ◽  
Inversion Layer ◽  
Hall Measurements ◽  
Temperature Range ◽  
Strong Inversion ◽  
Stark Contrast ◽  
Channel Region

Hall measurements on NO annealed 4H-SiC MOS gated Hall bars are reported in the temperature range 77 K- 423 K. The results indicate higher carrier concentration and lower trapping at increased temperatures, with a clear strong inversion regime at all temperatures. In stark contrast to Si, the Hall mobility increases with temperature for 77 K-373K, above which the mobility decreases slightly. The maximum experimental mobility was found to be ~50 cm2V-1s-1which is only about 10% of the 4H-SiC bulk mobility indicating that while NO annealing drastically improves trapping, it does not improve the mobility significantly. Supporting modeling results strongly suggest the presence of a disordered SiC channel region.

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