اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدMagnetism and local structure in low-dimensional, Mott insulating GdTiO3
178
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Cation displacements, oxygen octahedral tilts, and magnetism of epitaxial, ferrimagnetic, insulating GdTiO3 films sandwiched between cubic SrTiO3 layers are studied using scanning transmission electron microscopy and magnetization measurements. With decreasing GdTiO3 film thickness, structural (GdFeO3-type) distortions are reduced, concomitant with a reduction in the Curie temperature. Ferromagnetism persists to smaller deviations from the cubic perovskite structure than is the case for the bulk rare earth titanates. The results indicate that the FM ground state is controlled by the narrow bandwidth, exchange and orbital ordering, and only to second order depends on amount of the GdFeO3-type distortion.
قيم البحث
اقرأ أيضاً
V2O3 famously features all four combinations of paramagnetic vs antiferromagnetic, and metallic vs insulating states of matter in response to %-level doping, pressure in the GPa range, and temperature below 300 K. Using time-of-flight neutron spectro
scopy combined with density functional theory calculations of magnetic interactions, we have mapped and analyzed the inelastic magnetic neutron scattering cross section over a wide range of energy and momentum transfer in the chromium stabilized antiferromagnetic and paramagnetic insulating phases (AFI & PI). Our results reveal an important magnetic frustration and degeneracy of the PI phase which is relieved by the rhombohedral to monoclinic transition at $T_N=185$ K due to a significant magneto-elastic coupling. This leads to the recognition that magnetic frustration is an inherent property of the paramagnetic phase in $rm (V_{1-x}Cr_x)_2O_3$ and plays a key role in suppressing the magnetic long range ordering temperature and exposing a large phase space for the paramagnetic Mott metal-insulator transition to occur.
The magnetic structure of Ca$_2$MnReO$_6$ double perovskite is investigated by neutron powder diffraction and bulk magnetization, showing dominant non-collinear Mn magnetic moments [$4.35(7)$ $mu_B$] that are orthogonally aligned with the small Re mo
ments [$0.22(4)$ $mu_B$]. $Ab$-initio electronic structure calculations show that the strong spin-orbit coupling for Re $5d$ electrons combined with a relatively modest on-site Coulomb repulsion ($U_{eff}^{Re} gtrsim 0.6$ eV) is sufficient to render this material insulating. This is a rare example of spin-orbit assisted Mott insulator outside the realm of iridates, with remarkable magnetic properties.
We show theoretically the fingerprints of short-range spiral magnetic correlations in the photoemission spectra of the Mott insulating ground states realized in the triangular silicon surfaces K/Si(111)-B and SiC(0001). The calculated spectra present
low energy features of magnetic origin with a reduced dispersion ~10-40 meV compared with the center-of-mass spectra bandwidth ~0.2-0:3 eV. Remarkably, we find that the quasiparticle signal survives only around the magnetic Goldstone modes. Our findings would position these silicon surfaces as new candidates to investigate non-conventional quasiparticle excitations.
Identifying and characterizing the parent phases of iron-based superconductors is an important step towards understanding the mechanism for their high temperature superconductivity. We present an investigation into the magnetic interactions in the Mo
tt insulator La2O2Fe2OSe2. This iron oxyselenide adopts a 2-k magnetic structure with low levels of magnetic frustration. This magnetic ground state is found to be dominated by next-nearest neighbor interactions J2 and J2 and the magnetocrystalline anisotropy of the Fe2+ site, leading to 2D-Ising-like spin S=2 fluctuations. In contrast to calculations, the values are small and confine the spin excitations below ~ 25 meV. This is further corroborated by sum rules of neutron scattering. This indicates that superconductivity in related materials may derive from a weakly coupled and unfrustrated magnetic structure.
We describe the local structural properties of the iron oxychalcogenides, La$_2$O$_2$Fe$_2$O$M_2$ ($M$ = S, Se), by using pair distribution function (PDF) analysis applied to total scattering data. Our results of neutron powder diffraction show that
$M$ = S and Se possess similar nuclear structure at low and room temperatures. The local crystal structures were studied by investigating deviations in atomic positions and the extent of the formation of orthorhombicity. Analysis of the total scattering data suggests that buckling of the Fe$_2$O plane occurs below 100 K. The buckling may occur concomitantly with a change in octahedral height. Furthermore, within a typical range of 1-2 nm, we observed short-range orthorhombic-like structure suggestive of nematic fluctuations in both of these materials.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
