Physical Properties Of La₃MO₇:A First Principles Study

Transition metal oxides(TMOs)have been the hot topics in the fundamental research of condensed matter physics for several decades.Due to their strong correlation characteristics,TMOs have shown a lot of peculiar properties,such as high temperature superconductivity(HTSC),colossal magnetoresistivity(CMR),etc.Therefore,from the practical point of view,TMOs are widely expected to play an important role in the exploitation of new generation of devices.According to the effective electron orbital,TMOs can roughly be divided into 3d,4d and 5d groups.For 3d group,the local correlated electron interaction is very strong.However,compared with 3d elements,4d and 5d groups have relatively larger ionic radius,resulting in weaker coulomb interactions and larger band-gaps.So far,the studies about 3d TMOs are comprehensive,while 4d-and 5d-elements and their oxides have largely been ignored until the discovery of superconductivity in Sr2RuO4.Since then,the research enthusiasm for 4d and 5d TMOs has been inspired.It has been reported that 4d and 5d TMOs exhibit a variety of novel phenomena such as intricate magnetic patterns,dielectric properties and superconductivity in the previous work.More recently,iridium oxides have attracted growing attention,due to the influence of much stronger spin-orbit interactions on their physical properties while the interactions are very weak in 3d transition metal oxides.Specifically,the competing interactions present in the 4d-and 5d-oxides have the same intensity,including spin-orbit,coulomb and exchange interactions,which give rise to many unique properties that are absent in 3d system.In this article,first-principles calculations have been applied to systematically study the magnetic properties and doping effects of 4d and 5d TMOs.Now the main constants are shown as follows:In the first chapter,a brief introduction was given about TMOs to introduce its structures and basic properties,followed by a summary of Os group and Ir group TMO's studies.In the second chapter,the background knowledge of first-principles calculation,spin-orbit coupling effects,and polaron theory were briefly presented.Next,a brief summery about VASP package and maximally localized wannier functions were presented.In the third chapter,first-principles calculations have been performed to study the electronic structures of La3MO7(M=Ru and Os).Our theoretical results confirm that both of them are Mott insulating antiferromagnets with identical magnetic ordering.Moreover,doping research has also been carried out,the hole-doping effects and the possible polaron formation in hole-doped La3MO7 have been discussed systematicallyIn the forth chapter,a summary about our present work and an outlook on the future.