Quantifying the deleterious role of strong correlations inLa1−xCaxMnO3at the magnetocaloric transition

Abstract

Here we study orthorhombic La 1−x Ca x MnO 3 (LCMO) where x = 0.2, 0.25, and 0.3 measuring the magnetization, the magneto-Seebeck, and magnetovolume contraction as a function of temperature and magnetic field to examine the influence of lattice, spin, and electronic degrees of freedom. Making the assumption that these contributions are independent of each other allows us to isolate the purely magnetic contribution to the total entropy change. This is compared directly with the value predicted from a mean-field plus Bean-Rodbell model. The model allows the first order character of the transition to be determined, as well as assigning numeric values to the number of magnetic ions that make up preformed magnetic clusters, and to the magnitude of the spread in T C . We quantify how the clusters, the T C spread values, and the electronic contribution, impact deleteriously on the available entropy change in fixed magnetic field, as the first order nature of the transition strengthens.

On the nature of the (de)coupling of the magnetostructural transition in Er5 Si4

“…The difference obtained in Seebeck coefficients of both structures at 200 K was |𝑆 𝐷 𝑂(𝐼) − 𝑆 𝐷 𝑀 | ≈ 6 µV/K, which is in agreement with the experimental result that is in between ~ 6 and 7 µV/K [14]. Additionally, the electronic entropy change can be estimated from [26]:…”

“…, which is in agreement with the experimental result that is in between $6 and 7 mV K À1 [14]. Additionally, the electronic entropy change can be estimated from [26]…”

“…The difference obtained in Seebeck coefficients of both structures at 200 K was ≈ 6 μV K −1 , which is in agreement with the experimental result that is in between ∼6 and 7 μV K −1 . Additionally, the electronic entropy change can be estimated from where Δ S D is the previously calculated Seebeck coefficients difference, N is the carrier concentration, and e is the electronic charge. Considering that the Er ions are in the state Er 3+ , the percentage of electrons in the conduction band is ∼4.4%.…”

Off-axis electron holography of manganite-based heterojunctions: Interface potential and charge distribution

“…Manganite perovskite films are attractive materials due to their colossal magnetoresistance (CMR) effect, excellent magnetic-field-dependent rectifying characteristics and resulting potential applications. [1][2][3] In manganite, the strong magnetic-conductive coupling [4] and order-disorder transition of the spin, orbital, and charge degree of freedom [5] are severely depressed at a junction by strong interface/surface effect. Thus, the interfacial behavior has an important influence on the properties of thin-film heterojunctions and related devices.…”