Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userEvolution of magnetic phases and orbital occupation in (SrMnO3)n/(LaMnO3)2n superlattices
208
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The magnetic and electronic modifications induced at the interfaces in (SrMnO$_{3}$)$_{n}$/(LaMnO$_{3}$)$_{2n}$ superlattices have been investigated by linear and circular magnetic dichroism in the Mn L$_{2,3}$ x-ray absorption spectra. Together with theoretical calculations, our data demonstrate that the charge redistribution across interfaces favors in-plane ferromagnetic (FM) order and $e_{g}(x^{2}-y^{2})$ orbital occupation, in agreement with the average strain. Far from interfaces, inside LaMnO$_3$, electron localization and local strain favor antiferromagnetism (AFM) and $e_{g}(3z^{2}-r^{2})$ orbital occupation. For $n=1$ the high density of interfacial planes ultimately leads to dominant FM order forcing the residual AFM phase to be in-plane too, while for $n geq 5$ the FM layers are separated by AFM regions having out-of-plane spin orientation.
rate research
Read More
Superlattices of (LaMnO3)2n/(SrMnO3)n (n=1 to 5), composed of the insulators LaMnO3 and SrMnO3, undergo a metal-insulator transition as a function of n, being metallic for n<=2 and insulating for n>=3. Measurements of transport, magnetization and polarized neutron reflectivity reveal that the ferromagnetism is relatively uniform in the metallic state, and is strongly modulated in the insulating state, being high in LaMnO3 and suppressed in SrMnO3. The modulation is consistent with a Mott transition driven by the proximity between the (LaMnO3)/(SrMnO3) interfaces. Disorder localizes states at the Fermi level at the interfaces for n>=3. We suggest that this disorder is due to magnetic frustration at the interfaces.
We measure the optical conductivity of (SrMnO3)n/(LaMnO3)2n superlattices (SL) for n=1,3,5, and 8 and 10 < T < 400 K. Data show a T-dependent insulator to metal transition (IMT) for n leq 3, driven by the softening of a polaronic mid-infrared band. At n = 5 that softening is incomplete, while at the largest-period n=8 compound the MIR band is independent of T and the SL remains insulating. One can thus first observe the IMT in a manganite system in the absence of the disorder due to chemical doping. Unsuccessful reconstruction of the SL optical properties from those of the original bulk materials suggests that (SrMnO3)n/(LaMnO3)2n heterostructures give rise to a novel electronic state.
Manipulating the orbital state in a strongly correlated electron system is of fundamental and technological importance for exploring and developing novel electronic phases. Here, we report an unambiguous demonstration of orbital occupancy control between t2g and eg multiplets in quasi-twodimensional transition metal oxide superlattices (SLs) composed of a Mott insulator LaCoO3 and a band insulator LaAlO3. As the LaCoO3 sublayer thickness approaches its fundamental limit (i.e. one unit-cell-thick), the electronic state of the SLs changed from a Mott insulator, in which both t2g and eg orbitals are partially filled, to a band insulator by completely filling (emptying) the t2g (eg) orbitals. We found the reduction of dimensionality has a profound effect on the electronic structure evolution, which is, whereas, insensitive to the epitaxial strain. The remarkable orbital controllability shown here offers a promising pathway for novel applications such as catalysis and photovoltaics, where the energy of d level is an essential parameter.
CaBaFe4O7 is a mixed-valent transition metal oxide having both Fe2+ and Fe3+ ions in tetrahedral coordination. Here we characterize its magnetic properties by magnetization measurements and investigate its local electronic structure using soft x-ray absorption spectroscopy at the Fe L2,3 edges, in combination with multiplet cluster and spin-resolved band structure calculations. We found that the Fe2+ ion in the unusual tetrahedral coordination is Jahn-Teller active with the high-spin e^2 (up) t2^3 (up) e^1 (down) configuration having a x^2-y^2-like electron for the minority spin. We deduce that there is an appreciable orbital moment of about L_z=0.36 caused by multiplet interactions, thereby explaining the observed magnetic anisotropy. CaBaFe4O7, a member of the 114 oxide family, offers new opportunities to explore charge, orbital and spin physics in transition metal oxides.
The two-orbital double-exchange model is employed for the study of the magnetic and orbital orders in ($R$MnO$_3$)$_n$/($A$MnO$_3$)$_{2n}$ ($R$: rare earths; $A$: alkaline earths) superlattices. The A-type antiferromagnetic order is observed in a broad region of parameter space for the case of SrTiO$_3$ as substrate, in agreement with recent experiments and first-principles calculations using these superlattices. In addition, also a C-type antiferromagnetic state is predicted to be stabilized when using substrates like LaAlO$_3$ with smaller lattice constants than SrTiO$_3$, again in agreement with first principles results. The physical mechanism for the stabilization of the A- and C- magnetic transitions is driven by the orbital splitting of the $x^2-y^2$ and $3z^2-r^2$ orbitals. This splitting is induced by the $Q_3$ mode of Jahn-Teller distortions created by the strain induced by the substrates. In addition to the special example of (LaMnO$_3$)$_n$/(SrMnO$_3$)$_{2n}$, our phase diagrams can be valuable for the case where the superlattices are prepared employing narrow bandwidth manganites. In particular, several non-homogenous magnetic profiles are predicted to occur in narrow bandwidth superlattices, highlighting the importance of carrying out investigations in this mostly unexplored area of research.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
