La_(1-x)Sr_xMnO_3体系中Mn_3O_4微孪晶表征

Characterization of the Microtwinning of Mn_3O_4 in La_(1-x)Sr_xMnO_3 Compounds

La1-x Sr x MnO3(LSMO)锰氧化物由于具有显著的庞磁电阻效应而被广泛关注,但少量Mn3O4杂质相会破坏其磁电阻效应.采用透射电子显微术及其相关分析方法,系统表征了杂质相Mn3O4中的微孪晶结构,并分析其形成机制.研究发现,在具有锐钛矿结构的Mn3O4中,微孪晶的孪晶面为(112)面,且孪晶面附近含有少量Sr原子;孪晶面出现几率与Sr原子含量之间的关系表明,孪晶的形成归因于少量Sr原子降低了孪晶界面形成能,这有助于推测出从锐钛矿向钙钛矿发生结构演化的一般规律.

La1-xSrxMnO3 （LSMO） manganite has been widely focused on due to its significant colossal magnetoresistance （CMR） effect, but a trace of impurity Mn3 O4 suppresses the CMR effect. The microtwinning in Mn3O4 phase was characterized and its formation mechanism was analyzed systematically by means of transmission electron microscopy and the relative analytical methods. It was found that twin plane is defined as （112） and a small amount of Sr atoms are observed near the twin plane in Mn3 O4 with anatase structure. Based on the relationships between the probability of microtwinning and the number of Sr atoms, it can be verified that the formation of microtwinning may be attributed to the decrease in the formation energy of twin boundary induced by the introduction of Sr atoms, which contributes to deduce the general rule on the structural evolution from anatase to oerovskite.