The Phenomenon of Colossal Magnetoresistance and Some Experimental Results
Abstract
The Present material is anti ferromagnetic and insulting while replacing with alkaline earth atoms changes take place in symmetry and crystal structure. Ferromagnetic interaction for example increase with do pant concentration and attains maximum at, beyond this level different type of antiferromagnetic interaction intra as well as inter-layer emerge which grown the overall magnetic behavior of the compound. We discuss semi covalent exchange interactions of four types. The nature of exchange viewed with the degree of overlap of the empty level and the field level. Then most interesting case is where exchange between and take place through hopping of holes levels from to via. At each site the mobile hole spin is parallel to the localized case spin at and, thus, ferromagnetism is developed along bonds. This double exchange is strong enough to suppress other exchange interactions. In this paper we are discuss the fundamental aspects of the double-exchange interaction, the impact of other important features like john-Teller effect, modulation of bond length and angle through A-site substitution ,charge carrier transport dependence on A-site radius, orbital ordering among the - network etc. the colossal magneto resistance (CMR) phenomena arises due to several cause. The paper reviews various observed aspects related to CMR to contribute to latest understanding of its physics. Some experimental results are given to illustrate some aspects.