اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدAnisotropic Transport Properties of CeRu$_2$Al$_{10}$
121
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We studied the transport properties of CeRu_2Al_10 single crystals. All the transport properties show largely anisotropic behaviors below T_0. Those along the a- and c-axes show similar behaviors, but are different from those along the b-axis. This suggests that the system could be viewed as a two-dimensional system. The results of the thermal conductivity and thermoelectric power could be explained by assuming the singlet ground state below T_0. However, the ground state is not simple but has some kind of structure within a spin gap.
قيم البحث
اقرأ أيضاً
Magnetic ground state of Rh-doped Kondo semiconductor CeRu$_2$Al$_{10}$ [Ce(Ru$_{1-x}$Rh$_x$)$_2$Al$_{10}$] is investigated by muon-spin relaxation method. Muon-spin precession with two frequencies is observed in the $x$ = 0 sample, while only one fr
equency is present in the $x$ = 0.05 and 0.1 samples, which is attributed to the broad static field distribution at the muon site. The internal field at the muon site is enhanced from about 180 G in $x$ = 0 sample to about 800 G in the Rh-doped samples, supporting the spin-flop transition as suggested by macroscopic measurements, and the boundary of different magnetic ground states is identified around $x$ = 0.03. The drastic change of magnetic ground state by a small amount of Rh-doping (3%) indicates that the magnetic structure in CeRu$_2$Al$_{10}$ is not robust and can be easily tuned by external perturbations such as electron doping. The anomalous temperature dependence of internal field in CeRu$_2$Al$_{10}$ is suggested to be attributed to the hyperfine interaction between muons and conduction electrons.
A Kondo semiconductor CeRu$_2$Al$_{10}$ with an orthorhombic crystal structure shows an unusual antiferromagnetic ordering at rather high temperature $T_0$ of 27.3 K, which is lower than the Kondo temperature $T_{rm K}sim$ 60 K. In optical conductivi
ty [$sigma(omega)$] spectra that directly reflect electronic structure, the $c$-$f$ hybridization gap between the conduction and $4f$ states is observed at around 40 meV along the three principal axes. However, an additional peak at around 20 meV appears only along the $b$ axis. With increasing $x$ to 0.05 in Ce(Ru$_{1-x}$Rh$_x$)$_2$Al$_{10}$, the $T_0$ decreases slightly from 27.3 K to 24 K, but the direction of the magnetic moment changes from the $c$ axis to the $a$ axis. Thereby, the $c$-$f$ hybridization gap in the $sigma(omega)$ spectra is strongly suppressed, but the intensity of the 20-meV peak remains as strong as for $x=0$. These results suggest that the change of the magnetic moment direction originates from the decreasing of the $c$-$f$ hybridization intensity. The magnetic ordering temperature $T_0$ is not directly related to the $c$-$f$ hybridization but is related to the charge excitation at 20 meV observed along the $b$ axis.
We studied the physical properties of two Kondo-lattice compounds, CeRu$_2$As$_2$ and CeIr$_2$As$_2$, by a combination of electric transport, magnetic and thermodynamic measurements. They are of ThCr$_2$Si$_2$-type and CaBe$_2$Ge$_2$-type crystalline
structures, respectively. CeRu$_2$As$_2$ shows localized long-range antiferromagnetic ordering below $T_N$=4.3 K, with a moderate electronic Sommerfeld coefficient $gamma_0$=35 mJ/mol$cdot$K$^2$. A field-induced metamagnetic transition is observed near 2 T below $T_N$. Magnetic susceptibility measurements on aligned CeRu$_2$As$_2$ powders suggest that it has an easy axis and that the cerium moments align uniaxially along $mathbf{c}$ axis. In contrast, CeIr$_2$As$_2$ is a magnetically nonordered heavy-fermion metal with enhanced $gamma_0$$>$300 mJ/mol$cdot$K$^2$. The initial onset Kondo temperatures of the two compounds are respectively 6 K and 30 K. We discuss the role of the crystal structure to the strength of Kondo coupling. This work provides two new dense Kondo-lattice materials for further investigations on electronic correlation, quantum criticality and heavy-electron effects.
The orthorhombic compound NdFe$_2$Al$_{10}$ has been studied by powder and single-crystal neutron diffraction. Below $T_N$ = 3.9 K, the Nd$^{3+}$ magnetic moments order in a double-$k$ [$mathbf{k}_1 = (0, frac{3}{4}, 0)$, $mathbf{k}_2 = (0, frac{1}{4
}, 0)$] collinear magnetic structure, whose unit cell consists of four orthorhombic units in the $b$ direction.The refinements show that this structure consists of (0 1 0) ferromagnetic planes stacked along $b$, in which the moments are oriented parallel to $a$ (the easy anisotropy axis according to bulk magnetization measurements) and nearly equal in magnitude ($approx 1.7-1.9 mu_B$). The alternating 8-plane sequence providing the best agreement to the data turns out to be that which yields the lowest exchange energy if one assumes antiferromagnetic near-neighbor exchange interactions with $J_1 gg J_2, J_3$. With increasing temperature, the single-crystal measurements indicate the suppression of the $mathbf{k}_2$ component at $T = 2.7$ K, supporting the idea that the anomalies previously observed around 2--2.5 K result from a squaring transition. In a magnetic field applied along the $a$ axis, the magnetic Bragg satellites disappear at $H_c = 2.45$ T, in agreement with earlier measurements. Comparisons are made with related magnetic orders occurring in Ce$T_2$Al$_{10}$ ($T$: Ru, Os) and TbFe$_2$Al$_{10}$.
We report the discovery of CMA, a metal with strong magnetic anisotropy and moderate electronic correlations. Magnetization measurements find a Curie-Weiss moment of $0.83,mathrm{mu_B}$/Mn, significantly reduced from the Hunds rule value, and the mag
netic entropy obtained from specific heat measurements is correspondingly small, only $approx 9$ % of $R mathrm{ln},2$. These results imply that the Mn magnetism is highly itinerant, a conclusion supported by density functional theory calculations that find strong Mn-Al hybridization. Consistent with the layered nature of the crystal structure, the magnetic susceptibility $chi$ is anisotropic below 20 K, with a maximum ratio of $chi_{[010]}/chi_{[001]}approx 3.5$. A strong power-law divergence $chi(T)sim T^{-1.2}$ below 20 K implies incipient ferromagnetic order, and an Arrott plot analysis of the magnetization suggests a vanishingly low Curie temperature $T_Csim 0$. Our experiments indicate that CMA~is a rare example of a Mn-based weak itinerant magnet that is poised on the verge of ferromagnetic order.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
