Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userEffect of magnetism on lattice dynamics in metallic chromium
49
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Single-crystal sample of chromium doped with ca.0.2 at.%119Sn was studied by means of a transmission Mossbauer spectroscopy in the temperature range of 310-315 K. An anomaly in the temperature behavior of the center shift was found at ca. 313 K, a temperature that coincides well with the Neel temperature of chromium. The anomaly gives evidence that the vibrations of atoms in the studied system are affected by the magnetism.
rate research
Read More
We report the normal-state transport and magnetic properties of a pressure-induced superconductor CeTe$_{1.82}$. We found that the applied pressure is required to increase the Kondo temperature scale ($T^*_{rm K} sim$ 170 K), associated with the two-dimensional motion of the carriers confined within the Te plane. Both the short-range ferromagnetic ordering temperature ($T_{rm SRF} sim$ 6 K) and the long-range antiferromagnetic transition temperature ($T_{rm N} sim$ 4.3 K) are slightly increased with pressure. We suggest that the application of pressure enhances a coupling between the 4$f$ and conduction electrons. We also found that the field effect on the transport under pressure is analogous to that at ambient pressure, where a large magnetoresistance is observed in the vicinity of $T_{rm SRF}$.
We report the effect of hydrostatic pressure on the electronic state of the antiferromagnet UIrGe, which is isostructural and isoelectronic with the ferromagnetic superconductors UCoGe and URhGe. The Neel temperature decreases with increasing pressure. We constructed a p-T phase diagram and estimated the critical pressure pc, where the antiferromagnetism vanishes, as 12 GPa. The antiferromagnetic/paramagnetic transition appears to be first order.
Anomalies in the temperature dependences of the recoil-free factor, f, and the average center shift, <CS>, measured by 57-Fe Mossbauer Spectroscopy, were observed for the first time in the archetype of the sigma-phase alloys system, Fe-Cr. In both cases the anomaly started at the temperature close to the magnetic ordering temperature, and in both cases it was indicative of lattice vibrations hardening. As no magnetostrictive effects were found, the anomalies seem to be entirely due to a spin-phonon coupling. The observed changes in f and in <CS> were expressed in terms of the underlying changes in the potential, Delta E_p, and the kinetic energy, Delta E_k, respectively. The former, with the maximum value larger by a factor of six than the latter, decreases, while the latter increases with T. The total mechanical energy change, Delta E, was, in general, not constant, as expected for the Debye-like vibrations, but it resembled that of Delta E_p. Only in the range of 4-15 K, Delta E was hardly dependent on T.
We theoretically study the effect of electron-electron interactions on the metallic state of quasicrystals. To address the problem, we introduce the extended Hubbard model on the Ammann-Beenker tiling as a simple theoretical model. The model is numerically solved within an inhomogeneous mean-field theory. Because of the lack of periodicity, the metallic state is nonuniform in the electron density even in the noninteracting limit. We clarify how this charge distribution pattern changes with electron-electron interactions. We find that the intersite interactions change the distribution substantially and in an electron-hole asymmetric way. We clarify the origin of these changes through the analyses in the real and perpendicular spaces. Our results offer a fundamental basis to understand the electronic states in quasicrystalline metals.
Magnetic frustration in metals is scarce and hard to pinpoint, but exciting due to the possibility of the emergence of fascinating novel phases. The cubic intermetallic compound HoInCu$_4$ with all holmium atoms on an fcc lattice, exhibits partial magnetic frustration, yielding a ground state where half of the Ho moments remain without long-range order, as evidenced by our neutron scattering experiments. The substitution of In with Cd results in HoCdCu$_4$ in a full breakdown of magnetic frustration. Consequently we found a fully ordered magnetic structure in our neutron diffraction experiments. These findings are in agreement with the local energy scales and crystal electric field excitations, which we determined from specific heat and inelastic neutron scattering data. The electronic density of states for the itinerant bands acts as tuning parameter for the ratio between nearest-neighbor and next-nearest-neighbor interactions and thus for magnetic frustration.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
