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Register a new userLow-temperature physical properties of GdCoIn$_5$
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A comprehensive experimental and theoretical study of the low temperature properties of GdCoIn$_5$ was performed. Specific heat, thermal expansion, magnetization and electrical resistivity were measured in good quality single crystals down to $^4$He temperatures. All the experiments show a second-order-like phase transition at 30 K probably associated with the onset of antiferromagnetic order. Total energy GGA+U calculations indicate a ground state with magnetic moments localized at the Gd ions and allowed a determination of the Gd-Gd magnetic interactions. Band structure calculations of the electron and phonon contributions to the specific heat and Quantum Monte Carlo calculations of the magnetic contributions to the thermodynamic quantities reproduce quite well the experimental data.
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We present the result of an extended experimental characterization of the hexagonal intermetallic Haucke compound NpNi$_{5}$. By combining macroscopic and shell-specific techniques, we determine the 5$f$-shell occupation number $n_f$ close to 4 for the Np ions, together with orbital and spin components of the ordered moment in the ferromagnetic phase below T$_C$ = 16 K ($mu_{S}$ = -1.88~$mu_{B}$ and $mu_{L}$ = 3.91~$mu_{B}$). The apparent coexistence of ordered and disordered phases observed in the M{o}ssbauer spectra is explained in terms of slow relaxation between the components of a quasi-triplet ground state. The ratio between the expectation value of the magnetic dipole operator and the spin magnetic moment ($3langle T_{z}rangle/ langle S_{z}rangle$ = +1.43) is positive and large, suggesting a localized character of the 5$f$ electrons. The angular part of the spin-orbit coupling ($langlevec{ell}cdotvec{s}rangle$ = -5.55) is close to the value of -6.25 calculated for trivalent Np ions in intermediate coupling approximation. The results are discussed against the prediction of first-principle electronic structure calculations based on the spin-polarized local spin density approximation plus Hubbard interaction, and of a mean field model taking into account crystal field and exchange interactions.
We investigate the effects of an applied magnetic field on the magnetic properties of the antiferromagnet GdCoIn$_5$. The prominent anisotropy observed in the susceptibility below $T_N$ is rapidly suppressed by a field of just a few Tesla. Further evidence of this low energy-scale is obtained from magnetoresistance and magnetostriction experiments. The lattice lenght, particulary, shows a sudden change below 2 Tesla when the magnetic field is applied perpendicular to the crystallographic $hat{c}$-axis. The experimental results as a whole can be attributed to a small but non negligible higher-order crystalline electric field.
The low temperature, magnetic phase transition in LuFe2Ge2 is thought to be associated with itinerant magnetism. The effects of Y and Sc substitutions on the Lu site, as well as Ru and Co substitutions on the Fe site, on the low temperature magnetic phase transition of LuFe2Ge2 compound have been studied in single crystals via microscopic, thermodynamic and transport measurements. On one hand, Co substitution suppresses the transition below our base temperature of 2 K even at our lowest substitution level. On the other hand, Sc substitution enhances the transition temperature, and Y or Ru substitution suppresses the transition to lower temperature. Phase diagrams for Y, Sc and Ru substitutions have been constructed and the possibility of a unifying, composite diagram is discussed.
We present magnetic susceptibility, heat capacity, and neutron diffraction measurements of polycrystalline Nd2Ru2O7 down to 0.4 K. Three anomalies in the magnetic susceptibility measurements at 146, 21 and 1.8 K are associated with an antiferromagnetic ordering of the Ru4+ moments, a weak ferromagnetic signal attributed to a canting of the Ru4+ and Nd3+ moments, and a long-range-ordering of the Nd3+ moments, respectively. The long-range order of the Nd3+ moments was observed in all the measurements, indicating that the ground state of the compound is not a spin glass. The magnetic entropy of Rln2 accumulated up to 5 K, suggests the Nd3+ has a doublet ground state. Lattice distortions accompany the transitions, as revealed by neutron diffraction measurements, and in agreement with earlier synchrotron x-ray studies. The magnetic moment of the Nd3+ ion at 0.4 K is estimated to be 1.54(2){mu}B and the magnetic structure is all-in all-out as determined by our neutron diffraction measurements.
We have grown the new uranium compound URhIn$_5$ with the tetragonal HoCoGa$_5$-type by the In self flux method. In contrast to the nonmagnetic ground state of the isoelectronic analogue URhGa$_5$, URhIn$_5$ is an antiferromagnet with antiferromagnetic transition temperature $T_{rm N}$ = 98 K. The moderately large electronic specific heat coefficient $gamma$ = 50 mJ/K$^2$mol demonstrates the contribution of 5$f$ electrons to the conduction band. On the other hand, magnetic susceptibility in the paramagnetic state roughly follows a Curie-Weiss law with a paramagnetic effective moment corresponding to a localized uranium ion. The crossover from localized to itinerant character at low temperature may occur around the characteristic temperature 150 K where the magnetic susceptibility and electrical resistivity show a marked anomaly.
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