000226175 001__ 226175
000226175 005__ 20190509132606.0
000226175 0247_ $$2doi$$a10.5075/epfl-thesis-7547
000226175 02470 $$2urn$$aurn:nbn:ch:bel-epfl-thesis7547-0
000226175 02471 $$2nebis$$a10860630
000226175 037__ $$aTHESIS
000226175 041__ $$aeng
000226175 088__ $$a7547
000226175 245__ $$aSynthesis and Physical Properties of 3d, 4d and 5d Transition Metal Compounds
000226175 269__ $$a2017
000226175 260__ $$bEPFL$$c2017$$aLausanne
000226175 300__ $$a132
000226175 336__ $$aTheses
000226175 502__ $$aProf. Romuald Houdré (président) ; Prof. László Forró, Prof. Henrik Moodysson Rønnow (directeurs) ; Prof. Oleg V.  Yazyev, Prof. Johan Chang, Prof. Kazimierz Conder (rapporteurs)
000226175 520__ $$aIn this thesis I study the synthesis and basic physical properties characterization on 3$d$, 4$d$ and 5$d$ transition metal compounds.  Great success has been obtained in 3$d$ transition metal compounds, in which the electric states are well localized due to the large on-site Coulomb repulsion $U$. Most stoichiometric 3$d$ transition metal oxides are antiferromagnetic Mott insulators. Among them, low dimensional geometrically frustrated systems, such as $S$ = 1/2 Kagome lattice antiferromagnets, are at the forefront of condensed matter research. Recently, high-quality single crystals of $\mathrm{Cu_2OSO_4}$, which are spin-1/2 antiferromagnets with low dimensional magnetism, have been successfully synthesized. The measurements of specific heat, susceptibility and magnetization were performed on this material. We found that the Kagome-like compound $\mathrm{Cu_2OSO_4}$ shows typical signatures for a canted-AFM ground state with a weak ferromagnetic component.   On the other hand, $4d$ transition metal compounds were considered as weakly correlated systems because the electron correlation is expected to be weaker in $4d$ transition metal compounds compared with the $3d$ ones. The $4d$ ones naturally bridge two different regimes of the strongly correlated $3d$ compounds and the $5d$ compounds. Most notably, for instance, it is intriguing that seemingly similar $\mathrm{Ca_2RuO_4}$ and $\mathrm{Sr_2RuO_4}$ display totally different behavior: the former is a Mott insulator while the latter is metallic and becomes superconducting at low temperature. Here we report the synthesis of large single crystals of $\mathrm{MoPO_5}$, and present their magnetic and thermodynamic properties. We found that the $4d^1$ compound $\mathrm{MoPO_5}$ is orbitally quenched and orders into an antiferromagnet with the moments along $c$ axis. Spin-flop transition is observed which indicates magnetic anisotropy.  $5d$ orbitals are more extended and the Coulomb repulsion $U$ values are expected to be further reduced compared with those of $3d$ and $4d$ transition metal compounds. Thus, insulating behaviors in $5d$ transition metal compounds have been puzzling. A possible reason is the strong spin-orbit coupling. Here we show the ambient-pressure synthesis and physical properties of a new all-Ir$^{6+}$ iridate $\mathrm{Ba_8Al_2IrO_{14}}$ and a novel layered iridate $\mathrm{Ba_{21}Ir_9O_{43}}$. The synthesis, crystal structure, transport, and magnetic properties of them have been reported. $\mathrm{Ba_8Al_2IrO_{14}}$ is a $p-$type band insulator and shows antiferromagnetic couplings but display no order down to 2 K. $\mathrm{Ba_{21}Ir_9O_{43}}$ is an insulator with antiferromagnetic Curie-Weiss behavior, where a magnetic transition is suppressed down to low temperature of 9 K despite the large Curie-Weiss temperature of $-90$ K. We also performed the pressure-dependent resistivity measurements of the $5d$ compound $\mathrm{Ir_{0.95}Pt_{0.05}Te_{2}}$ and found that the charge order with $q$=(1/5,0,1/5) dimer configuration is introduced and the superconductivity undergoes a dimensionality cross-over from 3 dimension to 2 dimension under pressure.
000226175 6531_ $$aIridates
000226175 6531_ $$atransition metal compounds
000226175 6531_ $$aspin-orbital coupling
000226175 6531_ $$alow dimensional magnetism
000226175 6531_ $$asuperconductivity
000226175 700__ $$0247116$$g230109$$aYang, Lin
000226175 720_2 $$aForró, László$$edir.$$g105148$$0240227
000226175 720_2 $$aRønnow, Henrik Moodysson$$edir.$$g176429$$0243430
000226175 8564_ $$uhttps://infoscience.epfl.ch/record/226175/files/EPFL_TH7547.pdf$$zn/a$$s8600198$$yn/a
000226175 909C0 $$xU10142$$0252321$$pLPMC
000226175 909CO $$pthesis-bn2018$$pDOI$$pSB$$ooai:infoscience.tind.io:226175$$qDOI2$$qGLOBAL_SET$$pthesis
000226175 917Z8 $$x108898
000226175 917Z8 $$x108898
000226175 918__ $$dEDPY$$aSB
000226175 919__ $$aLPMC
000226175 920__ $$b2017$$a2017-3-10
000226175 970__ $$a7547/THESES
000226175 973__ $$sPUBLISHED$$aEPFL
000226175 980__ $$aTHESIS