Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userEffect of the Optical Pumping and Magnetic Field on the States of Phase Separation Domains in Eu_{0.8}Cr_{0.2}Mn_2O_5
48
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The effect of optical pumping and applied magnetic field on the characteristics of ferromagnetic layers in one-dimensional superlattices is studied. At low enough temperatures, these layers correspond to phase separation domains in RMn_2O_5 and R_{0.8}Ce_{0.2}Mn_2O_5 multiferroics. The formation of such domains occurs owing to the charge ordering of Mn^{3+} and Mn^{4+} ions and to the finite probability for e_g electrons to tunnel between these pairs of ions. The volume occupied by such superlattices is rather small, and they can be treated as isolated ferromagnetic semiconductor heterostructures, spontaneously formed in the host crystal. The sequences of ferromagnetic resonances related to the superlattice layers in Eu_{0.8}Ce_{0.2}Mn_2O_5 are studied. The characteristics of these resonances give information on the properties of such layers. For the first time, it is demonstrated that the optical pumping gives rise to a new metastable state of superlattices, which can be recovered by the magnetic field cycling to the state existing before the optical pumping. It is found that the superlattices recovered by the magnetic field exist up to temperatures higher than those in as-grown crystals.
rate research
Read More
We present a detailed magnetic study of the perovskite manganite Pr0.7Ca0.3MnO3 at low temperatures including magnetization and a.c. susceptibility measurements. The data appear to exclude a conventional spin glass phase at low fields, suggesting instead the presence of correlated ferromagnetic clusters embedded in a charge-ordered matrix. We examine the growth of the ferromagnetic clusters with increasing magnetic field as they expand to occupy almost the entire sample at H ~ 0.5 T. Since this is well below the field required to induce a metallic state, our results point to the existence of a field-induced ferromagnetic insulating state in this material.
We present La and Cu NMR relaxation measurements in single crystal La_{1.67}Eu_{0.2}Sr_{0.13}CuO_4. A strong peak in the La spin-lattice relaxation rate observed in the spin ordered state is well-described by the BPP mechanism[1] and arises from continuous slowing of electronic spin fluctuations with decreasing temperature; these spin fluctuations exhibit XY-like anisotropy in the ordered state. The spin pseudogap is enhanced by the static charge-stripe order in the LTT phase.
We have studied the temperature evolution of the inverse photoemission spectra of phase separated La$_{0.2}$Sr$_{0.8}$MnO$_{3}$. To identify the features in the room temperature experimental spectra, band structure calculations using Korringa-Kohn-Rostoker Greens function method were carried out. We find that the features generated by local moment disorder calculations give a better match with the experimental spectrum. In the insulating phase, we observed unusually an increased intensity at around the Fermi level. This puzzling behaviour is attributed to the shift in the chemical potential towards the conduction band. The present results clearly show the importance of unoccupied electronic states in better understanding of the phase separated systems.
The optical conductivity $sigma_{1}(omega)$ of Eu$_{1-x}$Ca$_{x}$B$_{6}$ has been obtained from reflectivity and ellipsometry measurements for series of compositions, $0leq xleq 1$. The interband part of $sigma_{1}(omega) $ shifts continuously to higher frequency as Ca-content $x$ increases. Also the intraband spectral weight of $sigma_{1}(omega)$ decreases rapidly and essentially vanishes for $xgeq x_{c}=0.35$. These results show that the valence band and the conduction band of Eu$_{1-x}$Ca$_{x}$B$_{6}$ move away from each other such that their band overlap decreases with increasing Ca-substitution. As a result, the electronic state evolves from the semimetallic structure of EuB$_{6}$ to the insulating CaB$_{6}$ where the two bands are separated to open a finite gap ($simeq 0.25$ eV) at the X-point of the Brillouin zone.
The specific heat C of Ce_{0.8}La_{0.2}Al_{3} has been measured as a function of temperature T in magnetic fields up to 14 T. A large peak in C at 2.3 K has recently been ascribed to an anisotropic Kondo effect in this compound. A 14-T field depresses the temperature of the peak by only 0.2 K, but strongly reduces its height. The corresponding peak in C/T shifts from 2.1 K at zero field to 1.7 K at 14 T. The extrapolated specific heat coefficient C/T(T->0) increases with field over the range studied. We show that these trends are inconsistent with the anisotropic Kondo model.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
