اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدFormation of metallic magnetic clusters in a Kondo-lattice metal: Evidence from an optical study
142
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Magnetic materials are usually divided into two classes: those with localised magnetic moments, and those with itinerant charge carriers. We present a comprehensive experimental (spectroscopic ellipsomerty) and theoretical study to demonstrate that these two types of magnetism do not only coexist but complement each other in the Kondo-lattice metal, Tb2PdSi3. In this material the itinerant charge carriers interact with large localised magnetic moments of Tb(4f) states, forming complex magnetic lattices at low temperatures, which we associate with self-organisation of magnetic clusters. The formation of magnetic clusters results in low-energy optical spectral weight shifts, which correspond to opening of the pseudogap in the conduction band of the itinerant charge carriers and development of the low- and high-spin intersite electronic transitions. This phenomenon, driven by self-trapping of electrons by magnetic fluctuations, could be common in correlated metals, including besides Kondo-lattice metals, Fe-based and cuprate superconductors.
قيم البحث
اقرأ أيضاً
The quantum phase transition between paramagnetic and antiferromagnetic phases of the Kondo lattice model with Ising anisotropy in the intersite exchange is studied within the framework of extended dynamical mean-field theory. Nonperturbative numeric
al solutions at zero temperature point to a continuous transition for both two- and three-dimensional magnetism. In the former case, the transition is associated with critical local physics, characterized by a vanishing Kondo scale and by an anomalous exponent in the dynamics close in value to that measured in heavy-fermion CeCu_{5.9}Au_{0.1}.
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 ma
gnetic 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.
We present the results of neutron diffraction studies on polycrystals of a metallic kagome lattice, Tb3Ru4Al12, reported recently to undergo reentrant magnetism, with the onset of long range antiferromagnetic order below (TN=) 22 K and spin-glass fea
tures below about 17 K. The present results reveal long-range antiferromagnetic order of an incommensurate type with the moments oriented along c-axis at all temperatures below TN. There are however notable changes in the T dependence of propagation vector along b-axis across 17 K. An observation of interest is that there is no decrease of intensity of magnetic Bragg peaks on entrance into the glassy phase (that is, below 17 K). This finding suggests that the magnetism of this compound is an exotic one and we wonder whether this compound is an example for dynamical spin-glass freezing phenomenon, as a consequence of geometrical frustration.
The magnetic ground state of the antiferromagnet Kondo lattice compound Ce8Pd24Ga has been investigated using neutron powder diffraction, inelastic neutron scattering and zero-field muon spin relaxation measurements. The neutron diffraction analysis,
below TN (3.6(0.2)K), reveals a commensurate type-C antiferromagnetic structure with the ordered state magnetic moment of ~0.36 mB/Ce-atom along the cubic <111> direction. The analysis of the inelastic neutron scattering (INS) data based on the crystal field (CF) model reveals a doublet ground state with a ground state moment of 1.29 mB/Ce-atom. The observed magnetic moment from neutron diffraction, which is small compared to the expected value from CF-analysis, is attributed to screening of the local Ce moment by the Kondo effect. This is supported by the observed Kondo-type resistivity and a small change in the entropy of Ce8Pd24Ga at TN. The zero-field muon spin relaxation rate exhibits a sharp increase below TN indicating ordering of Ce moments, in agreement with the neutron diffraction data. The present studies reveal that the physical properties of Ce8Pd24Ga are governed by the onsite Kondo compensation, the moment stabilizing intersite RKKY interaction and the crystal field effect.
We report neutron scattering experiments performed to investigate the dynamic magnetic properties of the Kondo-lattice compound YbNi2B2C. The spectrum of magnetic excitations is found to be broad, extending up to at least 150 meV, and contains inelas
tic peaks centred near 18 meV and 43 meV. At low energies we observe quasielastic scattering with a width Gamma = 2.1 meV. The results suggest a Yb3+ ground state with predominantly localized 4f electrons subject to (i) a crystalline electric field (CEF) potential, and (ii) a Kondo interaction, which at low temperatures is about an order of magnitude smaller than the CEF interaction. From an analysis of the dynamic magnetic response we conclude that the crystalline electric field acting on the Yb ions has a similar anisotropy to that in other RNi2B2C compounds, but is uniformly enhanced by almost a factor of 2. The static and dynamic magnetic properties of YbNi2B2C are found to be reconciled quite well by means of an approximation scheme to the Anderson impurity model, and this procedure also indicates that the effective Kondo interaction varies with temperature due to the crystal field splitting. We discuss the nature of the correlated-electron ground state of YbNi2B2C based on these and other experimental results, and suggest that this compound might be close to a quantum critical point on the non-magnetic side.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
