100 research outputs found
Electrocaloric Cooling
The electrocaloric effect describes a reversible temperature change in dielectric materials submitted to an applied electric field. Adiabatic polarization raises their temperature, and adiabatic depolarization lowers it, analogous to temperature changes that occur when a gas is compressed or expanded. For refrigerator application, the reverse Brayton cycle is currently the most promising for practical implementation. The electrocaloric effect provides a large material efficiency. However, existing refrigerator prototypes lack from the absence of efficient heat switches for thermal linkage to the load and the heat sink. Cooling power densities of a few W/cm2 and temperature spans in the order of 20 K (in regeneration systems) are achievable at a cycle time of 100 ms
Energiemanagement-Strategien fΓΌr batterieelektrische Fahrzeuge
Das Energiemanagement batterieelektrischer Fahrzeuge ist entscheidend, um das Potential der Batterie bestmΓΆglich auszunutzen. In dieser Arbeit werden daher die Anforderungen an das Energiemanagement herausgearbeitet und mathematisch als Optimierungsproblem beschrieben. Es werden Strategien vorgestellt, wie im Entwicklungsprozess mittels Dynamischer Programmierung und im Fahrbetrieb basierend auf dem Maximumprinzip alle wesentlichen EinflΓΌsse berΓΌcksichtigt werden kΓΆnnen
Energiemanagement-Strategien fΓΌr batterieelektrische Fahrzeuge
Das Energiemanagement batterieelektrischer Fahrzeuge ist entscheidend, um das Potential der Batterie bestmΓΆglich auszunutzen. In dieser Arbeit werden daher die Anforderungen an das Energiemanagement herausgearbeitet und mathematisch als Optimierungsproblem beschrieben. Es werden Strategien vorgestellt, wie im Entwicklungsprozess mittels Dynamischer Programmierung und im Fahrbetrieb basierend auf dem Maximumprinzip alle wesentlichen EinflΓΌsse berΓΌcksichtigt werden kΓΆnnen
ΠΡΠ΅Π½ΠΊΠ° ΡΡΠ΅ΠΏΠ΅Π½ΠΈ ΠΊΡΠΈΡΡΠ°Π»Π»ΠΎΠ³ΡΠ°ΡΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΡΠΏΠΎΡΡΠ΄ΠΎΡΠ΅Π½ΠΈΡ ΠΌΠ°Π³Π½ΠΈΡΠΎΠ°ΠΊΡΠΈΠ²Π½ΡΡ ΠΈΠΎΠ½ΠΎΠ² Π² Sr2FeMoO6-Ξ΄ Ρ ΠΏΠΎΠΌΠΎΡΡΡ ΠΈΠ½ΡΠ΅Π½ΡΠΈΠ²Π½ΠΎΡΡΠΈ ΡΠ΅Π½ΡΠ³Π΅Π½ΠΎΠ²ΡΠΊΠΎΠ³ΠΎ ΠΏΠΈΠΊΠ° (101)
Strontium ferromolybdate (Sr2FeMoO6-Ξ΄, SFMO) having a double Perovskite structure shows good promise as a basic material for spintronics. However SFMO has not yet found wide application due to the low reproducibility of its magnetic properties which partially originates from their strong dependence on the ordering degree of Fe and Mo ions in the BΒ΄ and BΒ² sublattices of double perovskite A2BΒ΄BΒ²O6. We have considered a rapid method of determining strontium ferromolybdate disorder degree. Sublattice population with Fe and Mo ions has been estimated for stoichiometric and nonstoichiometric Sr2FeMoO6-Ξ΄ with a 5% Fe and Mo excess, respectively. We have calculated the intensity ratio between the superstructural ordering (101) peak and the most intense (112 + 200) peak. The calculated curves have been fitted to the analytical expression for similar cases known from literature. The calculation results obtained using this method are in agreement with the results of experimental data processing using the Rietveld method accurate to within Β±25 %. Thus this method can be used instead of the Rietveld method if the exposure time set in an X-ray diffraction experiment is insufficient. We have discussed the dependence of the I(101)/I(112 + 200) peak intensity ratio on various factors including diffraction peak instrumental broadening, peak twinning due to grain size reduction, thin film lattice parameter variation due to substrate lattice mismatch and lattice parameter variation due to oxygen vacancies. The method is useful as it allows evaluating the superlattice ordering degree in Sr2FeMoO6-d without large time consumption for X-ray diffraction pattern recording and processing with the Rietveld method which may be essential when dealing with large amounts of experimental dataΠ€Π΅ΡΡΠΎΠΌΠΎΠ»ΠΈΠ±Π΄Π°Ρ ΡΡΡΠΎΠ½ΡΠΈΡ (Sr2FeMoO6-d, SFMO), ΠΎΠ±Π»Π°Π΄Π°ΡΡΠΈΠΉ ΡΡΡΡΠΊΡΡΡΠΎΠΉ Π΄Π²ΠΎΠΉΠ½ΠΎΠ³ΠΎ ΠΏΠ΅ΡΠΎΠ²ΡΠΊΠΈΡΠ°, ΡΠ²Π»ΡΠ΅ΡΡΡ ΠΌΠ½ΠΎΠ³ΠΎΠΎΠ±Π΅ΡΠ°ΡΡΠΈΠΌ ΠΊΠ°Π½Π΄ΠΈΠ΄Π°ΡΠΎΠΌ Π΄Π»Ρ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°Π½ΠΈΡ Π² ΠΊΠ°ΡΠ΅ΡΡΠ²Π΅ ΠΎΡΠ½ΠΎΠ²Π½ΠΎΠ³ΠΎ ΠΌΠ°ΡΠ΅ΡΠΈΠ°Π»Π° Π² ΡΠΏΠΈΠ½ΡΡΠΎΠ½ΠΈΠΊΠ΅. ΠΠ΄Π½Π°ΠΊΠΎ Π½Π° Π΄Π°Π½Π½ΡΠΉ ΠΌΠΎΠΌΠ΅Π½Ρ SFMO Π½Π΅ Π½Π°ΡΠ΅Π» ΡΠΈΡΠΎΠΊΠΎΠ³ΠΎ ΠΏΡΠΈΠΌΠ΅Π½Π΅Π½ΠΈΡ ΠΈΠ·-Π·Π° Π½ΠΈΠ·ΠΊΠΎΠΉ Π²ΠΎΡΠΏΡΠΎΠΈΠ·Π²ΠΎΠ΄ΠΈΠΌΠΎΡΡΠΈ Π΅Π³ΠΎ ΠΌΠ°Π³Π½ΠΈΡΠ½ΡΡ
ΡΠ²ΠΎΠΉΡΡΠ², Π²ΡΠ·Π²Π°Π½Π½ΠΎΠΉ, Π² ΡΠΎΠΌ ΡΠΈΡΠ»Π΅, ΠΈΡ
ΡΠΈΠ»ΡΠ½ΠΎΠΉ Π·Π°Π²ΠΈΡΠΈΠΌΠΎΡΡΡΡ ΠΎΡ ΡΡΠ΅ΠΏΠ΅Π½ΠΈ ΡΠΏΠΎΡΡΠ΄ΠΎΡΠ΅Π½ΠΈΡ ΠΊΠ°ΡΠΈΠΎΠ½ΠΎΠ² Fe ΠΈ Mo Π² ΠΏΠΎΠ΄ΡΠ΅ΡΠ΅ΡΠΊΠ°Ρ
BΒ΄ ΠΈ BΒ² Π΄Π²ΠΎΠΉΠ½ΠΎΠ³ΠΎ ΠΏΠ΅ΡΠΎΠ²ΡΠΊΠΈΡΠ° A2BΒ΄BΒ²O6. Π Π°ΡΡΠΌΠΎΡΡΠ΅Π½ ΡΠΊΡΠΏΡΠ΅ΡΡ-ΠΌΠ΅ΡΠΎΠ΄ ΠΎΠΏΡΠ΅Π΄Π΅Π»Π΅Π½ΠΈΡ ΡΡΠ΅ΠΏΠ΅Π½ΠΈ ΡΠ°Π·ΡΠΏΠΎΡΡΠ΄ΠΎΡΠ΅Π½ΠΈΡ ΡΠ΅ΡΡΠΎΠΌΠΎΠ»ΠΈΠ±Π΄Π°ΡΠ° ΡΡΡΠΎΠ½ΡΠΈΡ. Π‘ΡΠ΅ΠΏΠ΅Π½Ρ Π·Π°ΡΠ΅Π»Π΅Π½ΠΈΡ ΠΏΠΎΠ΄ΡΠ΅ΡΠ΅ΡΠΎΠΊ ΠΊΠ°ΡΠΈΠΎΠ½Π°ΠΌΠΈ Fe ΠΈ Mo ΠΎΠΏΡΠ΅Π΄Π΅Π»Π΅Π½Π° ΠΊΠ°ΠΊ Π΄Π»Ρ ΡΡΠ΅Ρ
ΠΈΠΎΠΌΠ΅ΡΡΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ, ΡΠ°ΠΊ ΠΈ Π΄Π»Ρ Π½Π΅ΡΡΠ΅Ρ
ΠΈΠΎΠΌΠ΅ΡΡΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ Sr2FeMoO6-Ξ΄ Ρ 5%-Π½ΡΠΌ ΠΈΠ·Π±ΡΡΠΊΠΎΠΌ Fe ΠΈ Mo ΡΠΎΠΎΡΠ²Π΅ΡΡΡΠ²Π΅Π½Π½ΠΎ. Π Π°ΡΡΡΠΈΡΠ°Π½ΠΎ ΡΠΎΠΎΡΠ½ΠΎΡΠ΅Π½ΠΈΠ΅ ΠΈΠ½ΡΠ΅Π½ΡΠΈΠ²Π½ΠΎΡΡΠΈ ΠΏΠΈΠΊa ΡΠ²Π΅ΡΡ
ΡΡΡΡΠΊΡΡΡΠ½ΠΎΠ³ΠΎ ΡΠΏΠΎΡΡΠ΄ΠΎΡΠ΅Π½ΠΈΡ (101) ΠΊ Π½Π°ΠΈΠ±ΠΎΠ»Π΅Π΅ ΠΈΠ½ΡΠ΅Π½ΡΠΈΠ²Π½ΠΎΠΌΡ ΠΏΠΈΠΊΡ (112 + 200). ΠΡΠΎΠ²Π΅Π΄Π΅Π½Π° ΠΏΠΎΠ΄Π³ΠΎΠ½ΠΊΠ° ΡΠ°ΡΡΠ΅ΡΠ½ΡΡ
ΠΊΡΠΈΠ²ΡΡ
ΠΏΠΎΠ΄ ΠΈΠ·Π²Π΅ΡΡΠ½ΠΎΠ΅ Π΄Π»Ρ Π°Π½Π°Π»ΠΎΠ³ΠΈΡΠ½ΡΡ
ΡΠ»ΡΡΠ°Π΅Π² Π°Π½Π°Π»ΠΈΡΠΈΡΠ΅ΡΠΊΠΎΠ΅ Π²ΡΡΠ°ΠΆΠ΅Π½ΠΈΠ΅. Π Π΅Π·ΡΠ»ΡΡΠ°ΡΡ ΡΠ°ΡΡΠ΅ΡΠΎΠ² ΠΏΡΠ΅Π΄Π»ΠΎΠΆΠ΅Π½Π½ΡΠΌ Π°Π²ΡΠΎΡΠ°ΠΌΠΈ ΠΌΠ΅ΡΠΎΠ΄ΠΎΠΌ ΡΠΎΠ²ΠΏΠ°Π΄Π°ΡΡ Ρ ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΠ°ΠΌΠΈ ΠΎΠ±ΡΠ°Π±ΠΎΡΠΊΠΈ ΡΠΊΡΠΏΠ΅ΡΠΈΠΌΠ΅Π½ΡΠ°Π»ΡΠ½ΡΡ
Π΄Π°Π½Π½ΡΡ
ΠΌΠ΅ΡΠΎΠ΄ΠΎΠΌ Π ΠΈΡΠ²Π΅Π»ΡΠ΄Π° Π² ΠΏΡΠ΅Π΄Π΅Π»Π°Ρ
Β±25 %, ΡΡΠΎ ΠΏΠΎΠ·Π²ΠΎΠ»ΡΠ΅Ρ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°ΡΡ ΡΡΠΎΡ ΠΌΠ΅ΡΠΎΠ΄ Π² ΠΊΠ°ΡΠ΅ΡΡΠ²Π΅ Π°Π»ΡΡΠ΅ΡΠ½Π°ΡΠΈΠ²Ρ ΠΌΠ΅ΡΠΎΠ΄Ρ Π ΠΈΡΠ²Π΅Π»ΡΠ΄Π° Π² ΡΠΎΠΌ ΡΠ»ΡΡΠ°Π΅, ΠΊΠΎΠ³Π΄Π° Π²ΡΠ΅ΠΌΡ Π²ΡΠ΄Π΅ΡΠΆΠΊΠΈ Π΄Π»Ρ ΡΠ΅Π½ΡΠ³Π΅Π½ΠΎΡΡΡΡΠΊΡΡΡΠ½ΠΎΠ³ΠΎ Π°Π½Π°Π»ΠΈΠ·Π° ΡΡΡΠ°Π½ΠΎΠ²Π»Π΅Π½ΠΎ Π½Π΅Π΄ΠΎΡΡΠ°ΡΠΎΡΠ½ΠΎ Π±ΠΎΠ»ΡΡΠΈΠΌ. ΠΠ±ΡΡΠΆΠ΄Π΅Π½ΠΎ Π²Π»ΠΈΡΠ½ΠΈΠ΅ ΡΠ°ΠΊΠΈΡ
ΡΠ°ΠΊΡΠΎΡΠΎΠ², ΠΊΠ°ΠΊ ΠΏΡΠΈΠ±ΠΎΡΠ½ΠΎΠ΅ ΡΡΠΈΡΠ΅Π½ΠΈΠ΅ Π΄ΠΈΡΡΠ°ΠΊΡΠΈΠΎΠ½Π½ΡΡ
ΠΏΠΈΠΊΠΎΠ², ΡΡΠΈΡΠ΅Π½ΠΈΠ΅ ΠΏΠΈΠΊΠΎΠ² Π²ΡΠ»Π΅Π΄ΡΡΠ²ΠΈΠ΅ ΡΠΌΠ΅Π½ΡΡΠ΅Π½ΠΈΡ ΡΠ°Π·ΠΌΠ΅ΡΠ° ΠΊΡΠΈΡΡΠ°Π»Π»ΠΈΡΠΎΠ², ΠΈΠ·ΠΌΠ΅Π½Π΅Π½ΠΈΠ΅ ΠΏΠ°ΡΠ°ΠΌΠ΅ΡΡΠΎΠ² ΡΠ΅ΡΠ΅ΡΠΊΠΈ ΡΠΎΠ½ΠΊΠΈΡ
ΠΏΠ»Π΅Π½ΠΎΠΊ Π·Π° ΡΡΠ΅Ρ ΠΈΡ
Π½Π΅ΡΠΎΠΎΡΠ²Π΅ΡΡΡΠ²ΠΈΡ Ρ ΠΏΠΎΠ΄Π»ΠΎΠΆΠΊΠΎΠΉ ΠΈ ΠΈΠ·ΠΌΠ΅Π½Π΅Π½ΠΈΠ΅ ΠΏΠ°ΡΠ°ΠΌΠ΅ΡΡΠΎΠ² ΡΠ΅ΡΠ΅ΡΠΊΠΈ Π·Π° ΡΡΠ΅Ρ ΠΏΠΎΡΠ²Π»Π΅Π½ΠΈΡ ΠΊΠΈΡΠ»ΠΎΡΠΎΠ΄Π½ΡΡ
Π²Π°ΠΊΠ°Π½ΡΠΈΠΉ Π½Π° ΡΠΎΠΎΡΠ½ΠΎΡΠ΅Π½ΠΈΠ΅ ΠΈΠ½ΡΠ΅Π½ΡΠΈΠ²Π½ΠΎΡΡΠΈ ΠΏΠΈΠΊΠΎΠ² I(101)/I(112 + 200). ΠΠΊΡΡΠ°Π»ΡΠ½ΠΎΡΡΡ ΠΌΠ΅ΡΠΎΠ΄Π° ΡΠΎΡΡΠΎΠΈΡ Π² ΡΠΎΠΌ, ΡΡΠΎ ΠΎΠ½ ΠΏΠΎΠ·Π²ΠΎΠ»ΡΠ΅Ρ ΠΎΡΠ΅Π½ΠΈΡΡ ΡΡΠ΅ΠΏΠ΅Π½Ρ ΡΠ²Π΅ΡΡ
ΡΡΡΡΠΊΡΡΡΠ½ΠΎΠ³ΠΎ ΡΠΏΠΎΡΡΠ΄ΠΎΡΠ΅Π½ΠΈΡ Sr2FeMoO6-d Π½Π΅ ΡΡΠ΅Π±ΡΡ Π±ΠΎΠ»ΡΡΠΈΡ
Π·Π°ΡΡΠ°Ρ Π²ΡΠ΅ΠΌΠ΅Π½ΠΈ ΡΡΠ΅ΠΌΠΊΠΈ ΠΈ ΠΎΠ±ΡΠ°Π±ΠΎΡΠΊΠΈ Π΄Π°Π½Π½ΡΡ
Π΄ΠΈΡΡΠ°ΠΊΡΠΎΠ³ΡΠ°ΠΌΠΌ ΠΌΠ΅ΡΠΎΠ΄ΠΎΠΌ Π ΠΈΡΠ²Π΅Π»ΡΠ΄Π°, ΡΡΠΎ ΠΌΠΎΠΆΠ΅Ρ Π±ΡΡΡ ΠΏΠΎΠ»Π΅Π·Π½ΠΎ Π² ΡΠ»ΡΡΠ°Π΅, ΠΊΠΎΠ³Π΄Π° ΠΏΡΠ΅Π΄ΡΡΠΎΠΈΡ ΠΎΠ±ΡΠ°Π±ΠΎΡΠ°ΡΡ Π±ΠΎΠ»ΡΡΠΎΠ΅ ΠΊΠΎΠ»ΠΈΡΠ΅ΡΡΠ²ΠΎ ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΠΎΠ² ΠΈΠ·ΠΌΠ΅ΡΠ΅Π½ΠΈΠΉ
ΠΠ°ΡΠ΅ΡΠΈΠ°Π»ΠΎΠ²Π΅Π΄ΡΠ΅ΡΠΊΠΈΠ΅ Π²ΠΎΠΏΡΠΎΡΡ ΡΠ΅ΡΠΌΠΎΠ΄ΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΌΠΎΠ΄Π΅Π»ΠΈΡΠΎΠ²Π°Π½ΠΈΡ ΡΠΎΠ½ΠΊΠΎΠΏΠ»Π΅Π½ΠΎΡΠ½ΡΡ ΡΠ²Π΅ΡΠ΄ΠΎΡΠ΅Π»ΡΠ½ΡΡ ΡΠ»Π΅ΠΊΡΡΠΎΠΊΠ°Π»ΠΎΡΠΈΡΠ΅ΡΠΊΠΈΡ ΠΎΡ Π»Π°Π΄ΠΈΡΠ΅Π»Π΅ΠΉ
Materials properties affecting EC device operation are discussed based on an analytically tractable model of a layered EC refrigerator. Special attention was paid to thermal and interface thermal resistances. Estimates of the average cooling power of a stacked MEMS-based EC refrigerator were made.ΠΠ»Π΅ΠΊΡΡΠΎΠΊΠ°Π»ΠΎΡΠΈΡΠ΅ΡΠΊΠΎΠ΅ ΠΎΡ
Π»Π°ΠΆΠ΄Π΅Π½ΠΈΠ΅ ΡΠ²Π»ΡΠ΅ΡΡΡ ΡΠΊΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΈ Π±Π΅Π·ΠΎΠΏΠ°ΡΠ½ΠΎΠΉ ΡΠ΅Ρ
Π½ΠΎΠ»ΠΎΠ³ΠΈΠ΅ΠΉ ΠΏΡΠ΅ΠΎΠ±ΡΠ°Π·ΠΎΠ²Π°Π½ΠΈΡ ΡΠ½Π΅ΡΠ³ΠΈΠΈ. ΠΠ»Π΅ΠΊΡΡΠΈΡΠ΅ΡΠΊΠΎΠ΅ ΠΏΠΎΠ»Π΅, Π½Π΅ΠΎΠ±Ρ
ΠΎΠ΄ΠΈΠΌΠΎΠ΅ Π΄Π»Ρ Π²ΠΎΠ·Π±ΡΠΆΠ΄Π΅Π½ΠΈΡ ΡΠΈΠΊΠ»Π° ΡΠ»Π΅ΠΊΡΡΠΎΠΊΠ°Π»ΠΎΡΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΎΡ
Π»Π°ΠΆΠ΄Π΅Π½ΠΈΡ, ΠΌΠΎΠΆΠ΅Ρ Π±ΡΡΡ ΡΠΎΠ·Π΄Π°Π½ΠΎ Π·Π½Π°ΡΠΈΡΠ΅Π»ΡΠ½ΠΎ ΠΏΡΠΎΡΠ΅ ΠΈ Ρ Π³ΠΎΡΠ°Π·Π΄ΠΎ ΠΌΠ΅Π½ΡΡΠΈΠΌΠΈ Π·Π°ΡΡΠ°ΡΠ°ΠΌΠΈ ΠΏΠΎ ΡΡΠ°Π²Π½Π΅Π½ΠΈΡ Ρ ΠΌΠ°Π³Π½ΠΈΡΠ½ΡΠΌΠΈ ΠΏΠΎΠ»ΡΠΌΠΈ, ΠΈΡΠΏΠΎΠ»ΡΠ·ΡΠ΅ΠΌΡΠΌΠΈ Π΄Π»Ρ ΠΌΠ°Π³Π½Π΅ΡΠΎΠΊΠ°Π»ΠΎΡΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΎΡ
Π»Π°ΠΆΠ΄Π΅Π½ΠΈΡ. ΠΡΠΎΠΌΠ΅ ΡΠΎΠ³ΠΎ, ΡΠ»Π΅ΠΊΡΡΠΈΡΠ΅ΡΠΊΠ°Ρ ΠΌΠΎΡΠ½ΠΎΡΡΡ, Π½Π΅ΠΎΠ±Ρ
ΠΎΠ΄ΠΈΠΌΠ°Ρ Π΄Π»Ρ ΡΠ»Π΅ΠΊΡΡΠΎΠΊΠ°Π»ΠΎΡΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΎΡ
Π»Π°ΠΆΠ΄Π΅Π½ΠΈΡ, ΠΌΠΎΠΆΠ΅Ρ ΠΎΠ±Π΅ΡΠΏΠ΅ΡΠΈΠ²Π°ΡΡΡΡ ΡΡΠ°ΡΠΈΠΎΠ½Π°ΡΠ½ΡΠΌΠΈ ΠΈΠ»ΠΈ ΠΌΠΎΠ±ΠΈΠ»ΡΠ½ΡΠΌΠΈ ΡΠΎΠ»Π½Π΅ΡΠ½ΡΠΌΠΈ Π±Π°ΡΠ°ΡΠ΅ΡΠΌΠΈ, Π° ΡΠ°ΠΊΠΆΠ΅ Π°ΠΊΠΊΡΠΌΡΠ»ΡΡΠΎΡΠ°ΠΌΠΈ ΡΠ»Π΅ΠΊΡΡΠΎΠΌΠΎΠ±ΠΈΠ»Ρ. ΠΡΠΎ ΠΎΡΠΊΡΡΠ²Π°Π΅Ρ ΡΠΎΠ²Π΅ΡΡΠ΅Π½Π½ΠΎ Π½ΠΎΠ²ΡΠ΅ Π²ΠΎΠ·ΠΌΠΎΠΆΠ½ΠΎΡΡΠΈ Π΄Π»Ρ ΡΠΊΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΈ Π±Π΅Π·ΠΎΠΏΠ°ΡΠ½ΠΎΠ³ΠΎ ΠΏΡΠΎΠΌΡΡΠ»Π΅Π½Π½ΠΎΠ³ΠΎ ΠΏΡΠΎΠ³ΡΠ΅ΡΡΠ° Π² ΡΠ°Π·Π²ΠΈΠ²Π°ΡΡΠΈΡ
ΡΡ ΡΡΡΠ°Π½Π°Ρ
. ΠΠ° ΠΎΡΠ½ΠΎΠ²Π΅ Π°Π½Π°Π»ΠΈΡΠΈΡΠ΅ΡΠΊΠΈ ΡΠ΅ΡΠ°Π΅ΠΌΠΎΠΉ ΠΌΠΎΠ΄Π΅Π»ΠΈ ΠΌΠ½ΠΎΠ³ΠΎΡΠ»ΠΎΠΉΠ½ΠΎΠ³ΠΎ ΡΠ»Π΅ΠΊΡΡΠΎΠΊΠ°Π»ΠΎΡΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΎΡ
Π»Π°Π΄ΠΈΡΠ΅Π»Ρ ΠΎΠ±ΡΡΠΆΠ΄Π΅Π½Ρ ΡΠ²ΠΎΠΉΡΡΠ²Π° ΠΌΠ°ΡΠ΅ΡΠΈΠ°Π»ΠΎΠ², Π²Π»ΠΈΡΡΡΠΈΠ΅ Π½Π° ΡΠΊΡΠΏΠ»ΡΠ°ΡΠ°ΡΠΈΠΎΠ½Π½ΡΠ΅ Ρ
Π°ΡΠ°ΠΊΡΠ΅ΡΠΈΡΡΠΈΠΊΠΈ ΡΠ»Π΅ΠΊΡΡΠΎΠΊΠ°Π»ΠΎΡΠΈΡΠ΅ΡΠΊΠΈΡ
ΠΏΡΠΈΠ±ΠΎΡΠΎΠ². ΠΡΠΎΠ±ΠΎΠ΅ Π²Π½ΠΈΠΌΠ°Π½ΠΈΠ΅ ΡΠ΄Π΅Π»Π΅Π½ΠΎ ΠΎΠ±ΡΠ΅ΠΌΠ½ΠΎΠΌΡ ΡΠ΅ΡΠΌΠΈΡΠ΅ΡΠΊΠΎΠΌΡ ΡΠΎΠΏΡΠΎΡΠΈΠ²Π»Π΅Π½ΠΈΡ ΠΈ ΡΠ΅ΡΠΌΠΈΡΠ΅ΡΠΊΠΎΠΌΡ ΡΠΎΠΏΡΠΎΡΠΈΠ²Π»Π΅Π½ΠΈΡ ΠΈΠ½ΡΠ΅ΡΡΠ΅ΠΉΡΠΎΠ². ΠΠ°Π½Ρ ΠΎΡΠ΅Π½ΠΊΠΈ ΡΡΠ΅Π΄Π½Π΅ΠΉ ΠΎΡ
Π»Π°ΠΆΠ΄Π°ΡΡΠ΅ΠΉ ΠΌΠΎΡΠ½ΠΎΡΡΠΈ ΡΡΠ΅ΠΊΠ° ΠΌΠΈΠΊΡΠΎΡΠ»Π΅ΠΊΡΡΠΎΠΌΠ΅Ρ
Π°Π½ΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΡΠ»Π΅ΠΊΡΡΠΎΠΊΠ°Π»ΠΎΡΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΎΡ
Π»Π°Π΄ΠΈΡΠ΅Π»Ρ
Magnetic-field-enhanced incommensurate magnetic order in the underdoped high-temperature superconductor YBa(2)Cu(3)O(6.45)
We present a neutron-scattering study of the static and dynamic spin
correlations in the underdoped high-temperature superconductor
YBa(2)Cu(3)O(6.45) in magnetic fields up to 15 T. The field strongly enhances
static incommensurate magnetic order at low temperatures and induces a
spectral-weight shift in the magnetic-excitation spectrum. A reconstruction of
the Fermi surface driven by the field-enhanced magnetic superstructure may thus
be responsible for the unusual Fermi surface topology revealed by recent
quantum-oscillation experiments.Comment: 4 pages, 3 figures. Version 2 as accepted by PRL, contains updated
reference list and improved comparison to similar effects in the La-214
syste
Stripes and Superconductivity in Cuprates
Holes doped into the CuO2 planes of cuprate parent compounds frustrate the
antiferromagnetic order. The development of spin and charge stripes provides a
compromise between the competing magnetic and kinetic energies. Static stripe
order has been observed only in certain particular compounds, but there are
signatures which suggest that dynamic stripe correlations are common in the
cuprates. Though stripe order is bad for superconducting phase coherence,
stripes are compatible with strong pairing. Ironically, magnetic-field-induced
stripe order appears to enhance the stability of superconducting order within
the planes.Comment: 6 pages, submitted to proceedings of ECRYS-201
Effects of impurities and vortices on the low-energy spin excitations in high-Tc materials
We review a theoretical scenario for the origin of the spin-glass phase of
underdoped cuprate materials. In particular it is shown how disorder in a
correlated d-wave superconductor generates a magnetic phase by inducing local
droplets of antiferromagnetic order which eventually merge and form a
quasi-long range ordered state. When correlations are sufficiently strong,
disorder is unimportant for the generation of static magnetism but plays an
additional role of pinning disordered stripe configurations. We calculate the
spin excitations in a disordered spin-density wave phase, and show how disorder
and/or applied magnetic fields lead to a slowing down of the dynamical spin
fluctuations in agreement with neutron scattering and muon spin rotation (muSR)
experiments.Comment: 4 pages, 3 figures, submitted for SNS2010 conference proceeding
Giant phonon anomalies and central peak due to charge density wave formation in YBaCuO
The electron-phonon interaction is a major factor influencing the competition
between collective instabilities in correlated-electron materials, but its role
in driving high-temperature superconductivity in the cuprates remains poorly
understood. We have used high-resolution inelastic x-ray scattering to monitor
low-energy phonons in YBaCuO (superconducting
K), which is close to a charge density wave (CDW) instability. Phonons in a
narrow range of momentum space around the CDW ordering vector exhibit extremely
large superconductivity-induced lineshape renormalizations. These results imply
that the electron-phonon interaction has sufficient strength to generate
various anomalies in electronic spectra, but does not contribute significantly
to Cooper pairing. In addition, a quasi-elastic "central peak" due to CDW
nanodomains is observed in a wide temperature range above and below ,
suggesting that the gradual onset of a spatially inhomogeneous CDW domain state
with decreasing temperature is a generic feature of the underdoped cuprates
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