Extension of instrumental capabilities in cryomagnetic laboratory

Měření elastických vlastností (teplotní roztažnosti a magnetostrikce) za multiextrémních podmínek je složitý úkol. V oblasti pokojové teploty nebo vyšší je dostupných několik metod, ale s klesající teplotou, aplikováním magnetického pole a aplikování hydrostatických tlaků je jejich počet omezen. Dilatometrické cely poskytují výbornou citlivost v nízkých teplotách a aplikovaných magnetických polích, nicméně nemohou být použity v tlakových celách. Nejčastější volba pro měření teplotní roztažnosti při aplikovaných hydrostatických tlacích jsou tenzometry. Ty mají průměrnou citlivost a zároveň je velice obtížné či nemožné je použít při nejnižších teplotách (T ≲ 3 K). Měření magnetických vlastností (zejména magnetizace) za multiextrémních podmínek je také složitý úkol. V oblasti teplot vyšších jak 2 K je dostupných několik metod, ale se snižující teplotou a aplikováním hydrostatických tlaků je jejich počet omezen. VSM poskytuje dobrou citlivost, ale nedá se použít v teplotách pod 2 K i při aplikovaných hydrostatických tlacích. MPMS aparatura je schopná měřit magnetizaci v tlaku až do 9 GPa (diamantová tlaková cela), ale nemůžeme aplikovat teploty nižší než 2 K. Naším záměrem je vyvinout citlivé měřící metody, které mohou být použity pro měření magnetizace a teplotní roztažnosti (magnetostrikce) při velice nízkých...Measurement of elastic properties (thermal expansion and magnetostriction) under (multi)extreme conditions is a difficult task. In the vicinity of the room temperature or above it an abundance of methods is available, with decreasing temperature and adding magnetic field and/or hydrostatic pressure their number is limited. Dilatometric cells (either planparaller or tilted plate design) provide superior sensitivity in low temperatures and applied magnetic fields, however, cannot be used in hydrostatic cell. Common choice for the measurement of thermal expansion under hydrostatic pressure are methods based on strain-gauges, with mediocre sensitivity and more importantly a difficult or even impossible usage at very low temperatures (T ≲ 3 K). Measurement of magnetic properties (especially magnetization) under (multi)extreme conditions is also a difficult task. In the vicinity of temperature 2 K and above it an abundance of methods is available, with decreasing temperature and adding magnetic field and/or hydrostatic pressure their number is limited. VSM system provides great sensitivity, but can not be used under 2 K and hydrostatic pressure. MPMS aparature provides pressure up to 9 GPa (diamond pressure cell), but still we can not apply lower temperatures than 2 K. Our aim is to develop a simple yet sensitive...Katedra fyziky kondenzovaných látekDepartment of Condensed Matter PhysicsMatematicko-fyzikální fakultaFaculty of Mathematics and Physic

Preparation of pure metals - analysis of the materials purity using physical quantities.

The thesis deals with the purity of lanthanoids and their purification using the solid state electrotransport (SSE). This method is used for high-level purification of metals. This process is really slow and is suitable especially for need of science. For this method we have prepared the cer and praseodym samples in monoarc and applicated SSE process on them. Afterthat we measured RRR (residual resistivity ratio) using four-point connection of the samples of cer and praseodym before and after the purification process and compared the values. The metals after SSE method always show a higher RRR value which means the lower level of impurities. Powered by TCPDF (www.tcpdf.org

Preparation of pure metals - analysis of the materials purity using physical quantities.

The thesis deals with the purity of lanthanoids and their purification using the solid state electrotransport (SSE). This method is used for high-level purification of metals. This process is really slow and is suitable especially for need of science. For this method we have prepared the cer and praseodym samples in monoarc and applicated SSE process on them. Afterthat we measured RRR (residual resistivity ratio) using four-point connection of the samples of cer and praseodym before and after the purification process and compared the values. The metals after SSE method always show a higher RRR value which means the lower level of impurities. Powered by TCPDF (www.tcpdf.org

Extension of instrumental capabilities in cryomagnetic laboratory

Measurement of elastic properties (thermal expansion and magnetostriction) under (multi)extreme conditions is a difficult task. In the vicinity of the room temperature or above it an abundance of methods is available, with decreasing temperature and adding magnetic field and/or hydrostatic pressure their number is limited. Dilatometric cells (either planparaller or tilted plate design) provide superior sensitivity in low temperatures and applied magnetic fields, however, cannot be used in hydrostatic cell. Common choice for the measurement of thermal expansion under hydrostatic pressure are methods based on strain-gauges, with mediocre sensitivity and more importantly a difficult or even impossible usage at very low temperatures (T ≲ 3 K). Measurement of magnetic properties (especially magnetization) under (multi)extreme conditions is also a difficult task. In the vicinity of temperature 2 K and above it an abundance of methods is available, with decreasing temperature and adding magnetic field and/or hydrostatic pressure their number is limited. VSM system provides great sensitivity, but can not be used under 2 K and hydrostatic pressure. MPMS aparature provides pressure up to 9 GPa (diamond pressure cell), but still we can not apply lower temperatures than 2 K. Our aim is to develop a simple yet sensitive..

Quantum ferromagnet in the proximity of the tricritical point

Echoes of quantum phase transitions at finite temperatures are theoretically and experimentally challenging and unexplored topics. Particularly in metallic quantum ferromagnets the experimental investigations are hampered by an intricate preparation of sufficiently pure samples and the access to the proper coordinates in parameter space. The present study shows that it is possible to tune a specific system at easily accessible conditions to the vicinity of its quantum phase transition. The physics is demonstrated on Ru-doped UCoAl, driven by pressure or substitution to and across the tricritical point and follows the first-order transition line to the theoretically presumed quantum phase transition. These findings open the possibilities for further in-depth studies of classical and quantum critical phenomena at easily reachable conditions