Magnetocaloric Effect in Manganites: Ferromagnetism and Charge- Ordering Effects
نویسندگان
چکیده
A study of the magnetocaloric properties of manganites with ferromagnetic and chargeordering states is presented. Under the application of a magnetic field in the vicinity of the paramagnetic-ferromagnetic and paramagnetic-charge order transitions large changes of the magnetic entropy are found, negative or positive, respectively. The physical mechanisms that contribute to the magnetic entropy and its temperature dependence are described and in the ferromagnetic case, discussed in terms of the Landau theory for phase transitions.
منابع مشابه
Entropy-Driven Reentrant Behavior in CMR Manganites
We discuss the origin of the reentrant behaviors of insulating states above the Curie temperature of the colossal magnetoresistance manganites. We consider a system where charge ordering and ferromagnetism compete with each other. In the presence of randomness which pins charge order fluctuations, entropy-driven reentrant behaviors will appear, which explains the typical temperature dependence ...
متن کاملReview of the magnetocaloric effect in manganite materials
A thorough understanding of the magnetocaloric properties of existing magnetic refrigerant materials has been an important issue in magnetic refrigeration technology. This paper reviews a new class of magnetocaloric material, that is, the ferromagnetic perovskite manganites (R1 xMxMnO3, where R 1⁄4 La, Nd, Pr and M 1⁄4 Ca, Sr, Ba, etc.). The nature of these materials with respect to their magne...
متن کاملFerromagnetism and Colossal Magnetoresistance from the Coexistence of Comparable Charge and Spin Density Orders
We report a complete multicomponent mean-field-theory for the coexistence and competition of charge ordering (CO), antiferromagnetic (AFM) and ferromagnetic (FM) spin ordering in the presence of a uniform magnetic field. Doping the AFM or CO state always generates a ferromagnetic component. Itinerant FM, AFM and CO, necessarily coexist and compete in a particle-hole asymmetric system. Melting o...
متن کاملFirst Principles Investigation of Ferromagnetism and Ferroelectricity in Bismuth Manganite
We present results of local spin density approximation (LSDA) pseudopotential calculations for the perovskite structure oxide, bismuth manganite (BiMnO3). The origin of the differences between bismuth manganite and other perovskite manganites is determined by first calculating total energies and band structures of the high symmetry cubic phase, then sequentially lowering the magnetic and struct...
متن کاملThe crucial role of mixed valence in the magnetoresistance properties of manganites and cobaltites.
The mixed valence Mn3+/Mn4+ and Co3+/Co4+ in manganites and cobaltites with the perovskite structure is absolutely necessary for the appearance of magnetotransport properties. It is shown that in these systems the Jahn Teller effect of the transition element, the charge and orbital ordering and the oxygen stoichiometry play a key role in the appearance of large and even colossal magnetoresistan...
متن کامل