Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userStructural and magnetic properties of antiferromagnetic Ce$_2$IrGa$_{12}$
113
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We report a study of the structural and magnetic properties of single crystals of Ce$_2$IrGa$_{12}$. Ce$_2$IrGa$_{12}$ crystallizes in a layered tetragonal structure, and undergoes an antiferromagnetic transition below 3.1 K. We characterize the temperature-field phase diagrams of Ce$_2$IrGa$_{12}$ for fields both within the $ab$-plane and along the $c$-axis, where the presence of a field-induced magnetic phase is found for in-plane fields. The ordering temperature is moderately enhanced upon the application of pressures up to 2.3~GPa, suggesting that Ce$_2$IrGa$_{12}$ corresponds to the well localized region of the Doniach phase diagram.
rate research
Read More
Structural, magnetization and heat capacity studies were performed on Ce$_2$(Pd$_{1-x}$Ni$_x$)$_2$Sn ($0 leq x leq 1$) alloys. The substitution of Pd atoms by isoelectronic Ni leads to a change in the crystallographic structure from tetragonal (for $x leq 0.3$) to centered orthorhombic lattice (for $x geq 0.4$). The volume contraction thorough the series is comparable to the expected from the atomic size ratio between transition metal components. The consequent weak increase of the Kondo temperature drives the two transitions observed in Ce$_2$Pd$_2$Sn to merge at $x = 0.25$. After about a 1% of volume collapse at the structural modification, the system behaves as a weakly magnetic heavy fermion with an enhanced degenerate ground state. Notably, an incipient magnetic transition arises on the Ni-rich size. This unexpected behavior is discussed in terms of an enhancement of the density of states driven by the increase of the $4f$-conduction band hybridization and the incipient contribution of the first excited crystal field doublet on the ground state properties.
The Ce(1-x)LaxCrGe3 (x = 0, 0.19, 0.43, 0.58 and 1) intermetallic compound system has been investigated by magnetization measurements and neutron scattering techniques to determine the effect of La-doping on the magnetic ordering and exchange interaction between Cr ions. The structural and magnetic characterization in this series was first verified by X-ray diffraction and bulk magnetization measurements. The samples exhibit the known hexagonal perovskite structure (P63/mmc space group) and have a single magnetic phase according to magnetization measurements. In this work, the ferromagnetic ordering temperature for Cr evolves smoothly from a range of 68 K to 77 K for CeCrGe3 to a range of 91 K to 96 K for LaCrGe3 as La replaces Ce. Magnetization results indicate the formation of domain walls below the transition temperature for all the Ce(1-x)LaxCrGe3 systems investigated. Neutron results indicate ordered magnetic Cr moments aligned along the c axis for the x = 1 LaCrGe3 system, as well as for x = 0.19, 0.43, and 0.58, which contrasts with the x = 0 CeCrGe3 where the moments order in the ab plane.
We report specific heat ($C$) and magnetization ($M$) of single crystalline Ce$_4$Pt$_{12}$Sn$_{25}$ at temperature down to $sim$50mK and in fields up to 3T. $C/T$ exhibits a sharp anomaly at 180mK, with a large $Delta C/Tsim$30J/molK$^2$-Ce, which, together with the corresponding cusp-like magnetization anomaly, indicates an antiferromagnetic (AFM) ground state with a Neel temperature $T_N$=180mK. Numerical calculations based on a Heisenberg model reproduce both zero-field $C$ and $M$ data, thus placing Ce$_4$Pt$_{12}$Sn$_{25}$ in the weak exchange coupling $J<J_c$ limit of the Doniach diagram, with a very small Kondo scale $T_Kll T_N$. Magnetic field suppresses the AFM state at $H^*approx$0.7T, much more effectively than expected from the Heisenberg model, indicating additional effects possibly due to frustration or residual Kondo screening.
We investigate the structural and magnetic properties of the new quantum magnet BaCuTe$_2$O$_6$. This compound is synthesized for the first time in powder and single crystal form. Synchrotron X-ray and neutron diffraction reveal a cubic crystal structure (P4$_1$32) where the magnetic Cu$^{2+}$ ions form a complex network. Physical properties measurements suggest the presence of antiferromagnetic interactions with a Curie-Weiss temperature of -33K, while long-range magnetic order occurs at the much lower temperature of ~6.3K. The magnetic structure, solved using neutron diffraction, reveals antiferromagnetic order along chains parallel to the a, b and c crystal axes. This is consistent with the magnetic excitations which resemble the multispinon continuum typical of the spin-1/2 Heisenberg antiferromagnetic chain. A consistent intrachain interaction value of ~34K is achieved from the various techniques. Finally the magnetic structure provides evidence that the chains are coupled together in a non-colinear arrangement by a much weaker antiferromagnetic, frustrated hyperkagome interaction.
Cerium-doped manganite thin films were grown epitaxially by pulsed laser deposition at $720 ^circ$C and oxygen pressure $p_{O_2}=1-25 $Pa and were subjected to different annealing steps. According to x-ray diffraction (XRD) data, the formation of CeO$_2$ as a secondary phase could be avoided for $p_{O_2}ge 8 $Pa. However, transmission electron microscopy shows the presence of CeO$_2$ nanoclusters, even in those films which appear to be single phase in XRD. With O$_2$ annealing, the metal-to-insulator transition temperature increases, while the saturation magnetization decreases and stays well below the theoretical value for electron-doped La$_{0.7}$Ce$_{0.3}$MnO$_3$ with mixed Mn$^{3+}$/Mn$^{2+}$ valences. The same trend is observed with decreasing film thickness from 100 to 20 nm, indicating a higher oxygen content for thinner films. Hall measurements on a film which shows a metal-to-insulator transition clearly reveal holes as dominating charge carriers. Combining data from x-ray photoemission spectroscopy, for determination of the oxygen content, and x-ray absorption spectroscopy (XAS), for determination of the hole concentration and cation valences, we find that with increasing oxygen content the hole concentration increases and Mn valences are shifted from 2+ to 4+. The dominating Mn valences in the films are Mn$^{3+}$ and Mn$^{4+}$, and only a small amount of Mn$^{2+}$ ions can be observed by XAS. Mn$^{2+}$ and Ce$^{4+}$ XAS signals obtained in surface-sensitive total electron yield mode are strongly reduced in the bulk-sensitive fluorescence mode, which indicates hole-doping in the bulk for those films which do show a metal-to-insulator transition.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
