ABSTRACT
We present a neutron scattering investigation of Ce1-xYxAl3 as a function of chemical pressure, which induces a transition from heavy-fermion behavior in CeAl3 (T{K}=5 K) to a mixed-valence state at x=0.5 (T{K}=150 K). The crossover can be modeled accurately on an absolute intensity scale by an increase in the k-f hybridization, V{kf}, within the Anderson impurity model. Surprisingly, the principal effect of the increasing V{kf} is not to broaden the low-energy components of the dynamic magnetic susceptibility but to transfer spectral weight to high energy.
ABSTRACT
The magnetic anisotropy parameters in [110] MBE-grown films of REFe(2) (RE, rare earth) compounds are not the same as those in the bulk. This is due to the presence of a shear strain ε(xy), frozen-in during crystal growth. In this paper, magnetic anisotropy parameters for [110] MBE-grown REFe(2) films, that directly involve the shear strain ε(xy), are presented and discussed. In addition to the usual first-order Callen and Callen term [Formula: see text], there are nine second-order terms, six of which involve cross-terms between ε(xy) and the cubic crystal field terms B(4) and B(6). Two of the second-order cross-terms are identified as being important: [Formula: see text] and [Formula: see text]. Of these, the rank-two term [Formula: see text] dominates over a large temperature range. It has the same angular dependence as the first-order term [Formula: see text], but with a more rapid temperature dependence. The correction at T = 0 K for TbFe(2), DyFe(2), HoFe(2), ErFe(2) and TmFe(2), amounts to â¼+9.2%, -13.9%, -11.6%, +14.3%, and 27.1%, respectively. Similar comments are made concerning the rank-four [Formula: see text] term.
ABSTRACT
We present inelastic neutron scattering experiments, performed near the antiferromagnetic quantum critical point in Ce(Ru0.24Fe0.76)2Ge2. Both local and long-range fluctuations of the local moments are observed, but due to the Kondo effect only the latter are critical. We propose a phenomenological expression which fits the energy E, temperature T, and wave vector q dependences of the dynamic susceptibility, describing the non-Fermi liquid E/T scaling found at every q.
ABSTRACT
By combining the results of muon spin relaxation and inelastic neutron scattering in the heavy fermion compounds Ce1-xLaxAl3 (0.0
ABSTRACT
We report for the first time, the observation of non-Fermi-liquid scaling behavior in an elemental paramagnetic metal. Both the dynamical susceptibility and the resistivity of beta-Mn are shown to display non-Fermi-liquid scaling over a relatively large temperature range at ambient pressure. The temperature dependence of the resistivity in beta-Mn is consistent with the existence of an antiferromagnetic zero-temperature phase transition or "quantum critical point." Since there is no site disorder in this pure element, we show that non-Fermi-liquid behavior observed in beta-Mn is not a consequence of summing over different local atomic environments, but a much more fundamental phenomenon.
ABSTRACT
We have used inelastic neutron scattering to determine the magnetic susceptibility chi(q,omega,T) of the non-Fermi-liquid compounds UCu(5-x)Pdx (x = 1,1.5) for energies omega between 0.2 and 2 meV, and for temperatures T between 1.6 and 250 K. Spatial correlations in both UCu4Pd and UCu 3.5Pd1.5 extend over length scales comparable to the unit cell, and display very little temperature dependence. In contrast, the wave vector independent susceptibility diverges as T-->0. We find that the excitations at all q, and for all T and omega accessed display the same type of non-Fermi-liquid omega/T scaling.
ABSTRACT
Neutron spectroscopic measurements of the magnetic excitations in PrO2 reveal (1) sharp peaks characteristic of transitions between levels of the 4f(1) configuration of Pr4+ split by the cubic crystal field, and (2) broad bands of scattering centered near 30 and 160 meV. We present a simple model based on a vibronic Hamiltonian that accounts for these contrasting features of the data. The analysis shows that 90%+/-10% of the Pr ions have a localized 4f(1) configuration and provides strong evidence for a dynamic Jahn-Teller effect in the gamma(8) electronic ground state.
