Inelastic neutron scattering study of CeNi2Ge2 (original) (raw)
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Magneto-crystalline Anisotropy and non-Fermi-liquid Behavior in CeNi1-xCoxGe2
Physics Procedia, 2015
We present results of magnetization, AC susceptibility and heat capacity measurements on polycrystalline CeNi1-xCoxGe2 samples (x = 0, 0.025, 0.05, 1) which were prepared by arc melting and on crystal CeNiGe2 grown by optical floating zone method in four mirror furnace. The parent compound CeNiGe2 is an antiferromagnetic Kondo system that orders magnetically at TN = 3.8 K and undergoes a spin structure rearrangement at T1 = 3.2 K while CeCoGe2 is a nonmagnetic heavyfermion Kondo compound with j = 5/2 ground state and large Kondo temperature TK > 200 K. Our measurements showed that the phase transition from the paramagnetic to the antiferromagnetic state was suppressed to lower temperatures with an increasing concentration of dopant.
Spin fluctuations and non-Fermi-liquid behavior of CeNi 2 Ge 2
Physical Review B, 2003
Neutron scattering shows that non-Fermi-liquid behavior of the heavy-fermion compound CeNi2Ge2 is brought about by the development of low-energy spin fluctuations with an energy scale of 0.6 meV. They appear around the antiferromagnetic wave vectors (1 2 1 2 0) and (00 3 4) at low temperatures, and coexist with high-energy spin fluctuations with an energy scale of 4 meV and a modulation vector (0.23, 0.23, 1 2). This unusual energy dependent structure of Imχ(Q, E) in Q space suggests that quasiparticle bands are important.
Inelastic neutron scattering study of cerium heavy fermion compounds
Journal of Magnetism and Magnetic Materials, 1988
We will review inelastic neutron scattering experiments performed on single crystals of the heavy fermion compounds CeRu2Si 2 and CeCu 6. At high temperatures, the magnetic scattering can be described by a single quasi-elastic Lorentzian peak. At low temperatures antiferro and incommensurate magnetic correlations develop below 70 and 10 K in CeRu 2Si2 and CeCu6, respectively; the associated wave vectors are k 1 (0.3, 0, 0) and k 2 = (0.3, 0.3, 0) for CeRu2Si 2 and k 1 ~ (0, 0, 1) and k 2-(0.85, 0, 0) for CeCu 6. These magnetic correlations are destroyed by a magnetic field applied along the easy axis (H, = 25 kOe for CeCu 6, H,=83 kOe for CeRu2Si2). These high field experiments allow" us to establish that in both compounds, at low T and H-0, the magnetic scattering is the superposition of two contributions: i) a q-independent (single site) quasi-elastic contribution of Lorentzian type, slowly decreasing at high field, ii) a strongly peaked inelastic contribution associated with magnetic correlations, centered at a finite energy he% with characteristic energy width I'~ h~o{} ~ 1.2 meV and 0.2 meV for CeRu2Si 2 and CeCu 6, respectively.
Magnetic form factor of the heavy fermion compounds CeCu2Ge2 and CeCu1.9Ni0.1Ge2
Physica B: Condensed Matter, 2003
CeCu 2 Ge 2 and CeCu 1.9 Ni 0.1 Ge 2 are heavy fermion compounds that order in incommensurate magnetic structures at low temperatures. The neutron magnetic form factor of single crystalline samples has been established by polarized neutron diffraction in the paramagnetic, as well as within the magnetically ordered state. For both compounds the neutron magnetic form factor could be reasonably well described within the dipole approximation but is also in accord with a G 7-ground state as proposed on the basis of inelastic neutron scattering experiments. The present polarized neutron diffraction study shows that the ordered magnetic moment of CeCu 2 Ge 2 is extremely stable against any change of temperature or magnetic field and further remains almost unaltered by alloying of 5% Ni.
Anomalous Low Temperature States in CeNi2Ge2
Arxiv preprint cond-mat/ …, 1998
Ambient pressure studies on high purity single crystals of the stoichiometric 4f-electron metal CeNi2Ge2 reveal anomalous low temperature forms of the resistivity which challenge our understanding of the metallic state. Comparisons are made with the isostructural and isoelectronic compound CePd2Si2 near the border of magnetism at high pressure, and possible reasons for this novel non-Fermi liquid form of the resistivity are discussed. Phase diagrams of further anomalies are presented, which involve a loss of resistance at low temperature in some samples of CeNi2Ge2 and unexpected high pressure phases.
Physical Review B, 2010
We report measurements of inelastic neutron scattering, magnetic susceptibility, magnetization, and the magnetic field dependence of the specific heat for the heavy Fermion compounds Ce3In and Ce3Sn. The neutron scattering results show that the excited crystal field levels have energies E1 = 13.2 meV, E2 = 44.8 meV for Ce3In and E1 = 18.5 meV, E2 = 36.1 meV for Ce3Sn. The Kondo temperature deduced from the quasielastic linewidth is 17 K for Ce3In and 40 K for Ce3Sn. The low temperature behavior of the specific heat, magnetization, and susceptibility can not be welldescribed by J=1/2 Kondo physics alone, but require calculations that include contributions from the Kondo effect, broadened crystal fields, and ferromagnetic correlations, all of which are known to be important in these compounds. We find that in Ce3In the ferromagnetic fluctuation makes a 10-15 % contribution to the ground state doublet entropy and magnetization. The large specific heat coefficient γ in this heavy fermion system thus arises more from the ferromagnetic correlations than from the Kondo behavior.
Physics Procedia, 2015
CeCu 2 Ge 2 , the counterpart of the heavy-fermion superconductor CeCu 2 Si 2 , exhibits an incommensurate antiferromagnetically long-range ordered ground state with τ = (0.28 0.28 0.54) below T N = 4.15 K. The magnetism is strongly affected by a Kondo screening of the Ce 4fmoments by conduction electrons. The similar energy scale of both, Kondo and exchange interactions, results in a complex magnetic phase diagram and gives rise to potential quantum critical phenomena at very low temperatures. We present elastic neutron diffraction data obtained on a CeCu 2 Ge 2 single crystal employing the cold triple axis spectrometer PANDA at MLZ and the diffractometer D23 at ILL. The field dependence of the magnetic propagation vector was measured at T ≤ 400 mK in the [110]/[001] plane with vertical magnetic fields applied along [110]. We observe a lowfield incommensurate magnetic phase AF1, a first order phase transition around 7.8 T with the coexistence of two phases AF1 and AF2 with slightly different propagation vectors, the disappearance of AF1 at 8 T and the existence of AF2 up to 12 T with a possible modification at 10 T. At 12.6 T, yet still well below the value of 26 T of the saturation for magnetic fields in [110] direction, the AF2-type magnetic order is lost and magnetic intensities are not to be found at incommensurate positions in the [110]/[001] plane any more. These new results contradict a previously suggested scenario with a QCP located at 8 T and contribute new information to the B − T phase diagram of CeCu 2 Ge 2 in [110] direction.
Anomalous low temperature states in CeNi2Ge2and CePd2Si2
Journal of Physics: Condensed Matter, 2000
High purity samples of the paramagnetic 4f-electron metal CeNi 2 Ge 2 exhibit a non-Fermi-liquid form of the resistivity ρ ∼ T x with x < 1.5 and decreasing towards 1 with increasing sample purity. Measurements of ρ versus T as a function of magnetic field and pressure show that this strange metallic phase is connected to the proximity of an antiferromagnetic quantum critical point as in the isoelectronic relative CePd 2 Si 2 near 2.8 GPa. The anomalous power-law dependence is surprisingly stable over extended ranges in temperature and pressure and challenges current theory of magnetic quantum phase transitions.
The low-temperature magnetism of cerium atoms in CeMn2Si2 and CeMn2Ge2 compounds
Journal of Physics: …, 2004
The low-temperature magnetic properties of the Ce atoms in the intermetallic compounds CeMn 2 Ge 2 and CeMn 2 Si 2 were studied. Previous neutron scattering measurements did not detect an ordered moment at Ce atoms in either compound despite the fact that they are surrounded by the Mn moments ordered ferromagnetically in the CeMn 2 Ge 2 and antiferromagnetically in the CeMn 2 Si 2 . Contrasting with this result, a recent measurement performed with the time differential perturbed angular correlation (TDPAC) technique showed the presence of a pronounced magnetic hyperfine field (MHF) at Ce sites in the CeMn 2 Ge 2 compound and no MHF in CeMn 2 Si 2 . The absence of the Ce magnetic moment and MHF in the silicide can be understood in terms of too weak a Ce-Ce magnetic interaction while in the germanide the TDPAC result suggests that some magnetic ordering of Ce atoms may occur. Aiming to understand the effects which result in the quenching of the Ce 4f moment in both cases, we performed first-principles band-structure calculations for both systems, using the full potential linear augmented plane wave method. It is shown that the magnetism of the Ce sublattice has fundamentally different nature in CeMn 2 Si 2 and CeMn 2 Ge 2 . While the Ce atoms are intrinsically nonmagnetic in the silicide, having a zero magnetic moment with both spin and orbital contributions identically zero, they display magnetic properties in the CeMn 2 Ge 2 since their very small total moment is composed of finite spin and orbital components which almost cancel each other accidentally.
Applied Physics A, 2017
We report our studies of the intermediate compositions between CeNi 2 Si 2 and CeNi 2 Ge 2 , i.e., the alloys CeNi 2 (Si 1-y Ge y) 2 by means of the thermopower, electrical resistivity, specific heat, magnetic susceptibility, and X-ray photoemission measurements. CeNi 2 Si 2 is a fluctuating valence system and CeNi 2 Ge 2 is known to show the heavy fermion behaviour. The change of the temperature dependence of the resistivity towards the typical metallic behaviour occurs below y 0.25. The transition between CeNi 2 Si 2 and CeNi 2 Ge 2 is discussed in the frames of competition between the crystal electric field and Kondo interactions. It is found that valence stabilisation occurs for Ge content y [ 0.25. The hybridization energy Δ determined from the XPS Ce 3d spectrum reflects well the behaviour of the parameter E ex obtained from the analysis of the magnetic susceptibility by the interconfiguration fluctuation model. It has been also shown that thermopower data can be successfully described employing the single ion model for 0.6 \ y \ 1.0 and two-band model including the crystal electric field splitting for y ≤ 0.25.