High Pressure Measurements on TI2Mn2O7

1999 ◽  
Vol 602 ◽  
Author(s):  
M. Núñez-Regueiro ◽  
R. Senis ◽  
W. Cheikh-Rouhou ◽  
P. Strobel ◽  
P. Bordet ◽  
...  
Keyword(s):  
High Pressure ◽  
Transition Temperature ◽  
Pressure Dependence ◽  
Colossal Magnetoresistance ◽  
Structural Changes ◽  
Structural Parameters ◽  
Applied Pressure ◽  
Ferromagnetic Transition ◽  
Pressure Measurements ◽  
Electronic Band

AbstractTransport and structural properties of the colossal magnetoresistance pyrochlore TI2Mn2O7 are studied as a function of applied pressure up to ∼20GPa. This allows us to probe the effect of structural changes on the ferromagnetic transition and the transport properties. We observe a non-monotonous pressure dependence of the ferromagnetic transition temperature. We correlate this unusual variation with the structural parameters that, according to electronic band calculations, are key in controlling the properties of these materials.

Effect of Zn substitution on para- to ferromagnetic transition temperature in La0.67Ca0.33Mn1−xZnxO3 colossal magnetoresistance materials

2000 ◽  
Vol 87 (9) ◽  
pp. 5034-5036 ◽  
Author(s):  
V. P. S. Awana ◽  
E. Schmitt ◽  
E. Gmelin ◽  
Anurag Gupta ◽  
A. Sedky ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Colossal Magnetoresistance ◽  
Ferromagnetic Transition ◽  
Zn Substitution

scholarly journals High temperature superconductivity in sulfur hydride under ultrahigh pressure: A complex superconducting phase beyond conventional BCS

2016 ◽  
Vol 2 (1) ◽  
Author(s):  
Annette Bussmann-Holder ◽  
Jürgen Köhler ◽  
M.-H. Whangbo ◽  
Antonio Bianconi ◽  
Arndt Simon
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Transition Temperature ◽  
Hydrogen Bonds ◽  
Pressure Dependence ◽  
High Temperature Superconductivity ◽  
Superconducting Phase ◽  
Ultrahigh Pressure ◽  
Phonon Modes ◽  
Interband Coupling

AbstractThe recent report of superconductivity under high pressure at the record transition temperature of Tc =203 K in pressurized H2S has been identified as conventional in view of the observation of an isotope effect upon deuteration. Here it is demonstrated that conventional theories of superconductivity in the sense of BCS or Eliashberg formalisms cannot account for the pressure dependence of the isotope coefficient. The only way out of the dilemma is a multi-band approach of superconductivity where already small interband coupling suffices to achieve the high values of Tc together with the anomalous pressure dependent isotope coefficient. In addition, it is shown that anharmonicity of the hydrogen bonds vanishes under pressure whereas anharmonic phonon modes related to sulfur are still active.

Simulation of Structural Parameters and Superconducting Transition Temperature of MgB2 under Pressure

2005 ◽  
Vol 475-479 ◽  
pp. 3319-3322
Author(s):  
Yang Shao ◽  
X. Zhang ◽  
Fu Ling Tang
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Transition Temperature ◽  
Superconducting Transition Temperature ◽  
Pressure Effect ◽  
Structural Parameters ◽  
Experimental Results ◽  
Bcs Theory ◽  
Superconducting Transition ◽  
Potential Parameters

We successfully developed the potential parameters for simulation of MgB2. With these potential parameters, we calculate the lattice parameters and volume variations with pressure up to 240GPa. All these results agree well with experimental data under 40GPa and provide reasonable tendencies from 40GPa to 240GPa. By employing the McMillan expression, it is found that the lattice stiffening dominants the behavior of Tc under pressure in the scope of BCS theory. Using our calculated Grüneisen parameter G g , the simulated pressure effect on Tc accords well with experimental results. Our result shows that the Tc of MgB2 can be destroyed by high pressure.

Variation of the pressure dependence of the superconducting transition temperature with x in La1−xSrx CuO4

1987 ◽  
Vol 2 (4) ◽  
pp. 421-423 ◽  
Author(s):  
J. E. Schirber ◽  
E. L. Venturini ◽  
J. F. Kwak ◽  
D. S. Ginley ◽  
B. Morosin
Keyword(s):  
Transition Temperature ◽  
Hydrostatic Pressure ◽  
Band Structure ◽  
Pressure Dependence ◽  
Superconducting Transition Temperature ◽  
Sharp Change ◽  
Pressure Measurements ◽  
Superconducting Transition ◽  
Pressure Derivative

Hydrostatic pressure measurements of the superconducting transition temperature were made as a function of x in La2−xSrx CuO4. A sharp change in the behavior occurs between x = 0.2 and 0.25 in that the pressure derivative goes from positive to essentially zero. This result is discussed in the context of band structure models.

ISOTOPE EFFECTS OF Mn AND O IN COLOSSAL MAGNETORESISTIVE MANGANITES

2005 ◽  
Vol 19 (30) ◽  
pp. 4427-4436
Author(s):  
JE HUAN KOO ◽  
GUANGSUP CHO
Keyword(s):  
Transition Temperature ◽  
Curie Temperature ◽  
Colossal Magnetoresistance ◽  
Manganese Oxides ◽  
Isotope Effects ◽  
Kondo Lattice ◽  
Ferromagnetic Transition ◽  
Colossal Magnetoresistive ◽  
Kondo Lattice Model ◽  
Peierls Transition

We investigate theoretically manganese oxides where the colossal magnetoresistance (CMR) is observed. We obtain the Curie temperature Tc using a Kondo lattice model for paramagetic to ferromagnetic transition. We also acquire the charge-ordered transition temperature TCO applying spin-Peierls transition. We calculate the isotope exponents of Mn ion and O ion such as αc for Tc and αCO for TCO. Calculated αc of O ion is less than 0.9 and αCO is ~-(0.1~0.9).

High-pressure DTA Studies of the Phase Behaviors of 4-n -butyl-thiocyanobiphenyl (4TCB) and 4-w-pentyl-4’-n-phenyl-cyanocyclohexane (5HCP)

1999 ◽  
Vol 54 (12) ◽  
pp. 675-678 ◽  
Author(s):  
M. Massalska-Arodź ◽  
A. Würflinger ◽  
D. Büsinga
Keyword(s):  
High Pressure ◽  
Liquid Crystal ◽  
Transition Temperature ◽  
Pressure Dependence ◽  
Nematic Phase ◽  
Liquid Crystalline ◽  
Melting Curve ◽  
Liquid Crystal Phase ◽  
Dta Studies ◽  
Phase Behaviors

Abstract DTA measurements of 4-n-butyl-thiocyanobiphenyl (4TCB) and ρ-cyano-ρ’-pentylphenyl-cyclohex-ane (5HCP) have been performed in the temperature range 220 K-390 K and pressures up to 400 MPa. For 4TCP a transition from a crystalline to a liquid crystal phase (probably smectic E) could be detect-ed at higher pressures > 90 MPa. The pressure dependence of the transition temperature has been estab-lished. At pressures lower than 88.7 MPa no transition of SmE into a crystal or into a glass has been found. For 5HCP only the melting curve was observed, in contrast to 5PCH, which displays a liquid crystalline nematic phase.

Analysis of the Deformation Behaviour of Cu Processed by High Pressure Torsion

2006 ◽  
Vol 114 ◽  
pp. 101-108 ◽  
Author(s):  
Vil D. Sitdikov ◽  
Roza G. Chembarisova ◽  
Igor V. Alexandrov
Keyword(s):  
High Pressure ◽  
Structural Changes ◽  
High Pressure Torsion ◽  
Deformation Behaviour ◽  
Applied Pressure ◽  
Dislocation Model ◽  
Sources And Sinks ◽  
Dislocation Sources ◽  
Pure Cu ◽  
Misorientation Angles

In the investigation the 3D version of the Estrin-Tóth dislocation model was used to analyze deformation behaviour of pure Cu, subjected to high pressure torsion (HPT) under pressures equal to 0.8, 2, 5, 8 GPa. As a result of the computer simulation, the nature and reasons for strain hardening are analyzed, the dislocation density evolution versus degree of SPD and graincell size versus degree of SPD curves were plotted. It is shown that the model adequately reflects the acting deformation mechanisms and structural changes during HPT at different applied pressures. It has been stated that an increase of the applied pressure at HPT leads to an increase in the activity of dislocation sources and sinks in the grain-cell walls. Misorientations between boundaries are estimated. It is revealed that an increase of the applied pressure contributes to a growth of the misorientation angles between neighbouring grain-cells.

scholarly journals Using applied pressure to guide materials design: a neutron diffraction study of La2NiO4+δ and Pr2NiO4+δ

2020 ◽  
Vol 49 (30) ◽  
pp. 10631-10637
Author(s):  
Craig L. Bull ◽  
Christopher J. Ridley ◽  
Helen Y. Playford
Keyword(s):  
High Pressure ◽  
Neutron Diffraction ◽  
Diffraction Study ◽  
Structural Changes ◽  
Applied Pressure ◽  
Materials Design ◽  
Neutron Diffraction Study

High-pressure structural changes being used as a guide to materials design.

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