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تسجيل مستخدم جديدFragile antiferromagnetism in the heavy-fermion compound YbBiPt
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We report results from neutron scattering experiments on single crystals of YbBiPt that demonstrate antiferromagnetic order characterized by a propagation vector, $tau_{rm{AFM}}$ = ($frac{1}{2} frac{1}{2} frac{1}{2}$), and ordered moments that align along the [1 1 1] direction of the cubic unit cell. We describe the scattering in terms of a two-Gaussian peak fit, which consists of a narrower component that appears below $T_{rm{N}}~approx 0.4$ K and corresponds to a magnetic correlation length of $xi_{rm{n}} approx$ 80 $rm{AA}$, and a broad component that persists up to $T^*approx$ 0.7 K and corresponds to antiferromagnetic correlations extending over $xi_{rm{b}} approx$ 20 $rm{AA}$. Our results illustrate the fragile magnetic order present in YbBiPt and provide a path forward for microscopic investigations of the ground states and fluctuations associated with the purported quantum critical point in this heavy-fermion compound.
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We present neutron diffraction data for the cubic-heavy-fermion YbBiPt that show broad magnetic diffraction peaks due to the fragile short-range antiferromagnetic (AFM) order persist under an applied magnetic-field $mathbf{H}$. Our results for $mathb
f{H}perp[bar{1}~1~0]$ and a temperature of $T=0.14(1)$ K show that the $(frac{1}{2},frac{1}{2},frac{3}{2})$ magnetic diffraction peak can be described by the same two-peak lineshape found for $mu_{0}H=0$ T below the N{e}el temperature of $T_{text{N}}=0.4$ K. Both components of the peak exist for $mu_{0}Hlesssim1.4 T$, which is well past the AFM phase boundary determined from our new resistivity data. Using neutron diffraction data taken at $T=0.13(2)$ K for $mathbf{H}parallel[0~0~1]$ or $[1~1~0]$, we show that domains of short-range AFM order change size throughout the previously determined AFM and non-Fermi liquid regions of the phase diagram, and that the appearance of a magnetic diffraction peak at $(frac{1}{2},frac{1}{2},frac{1}{2})$ at $mu_{0}Happrox0.4$ T signals canting of the ordered magnetic moment away from $[1~1~1]$. The continued broadness of the magnetic diffraction peaks under a magnetic field and their persistence across the AFM phase boundary established by detailed transport and thermodynamic experiments present an interesting quandary concerning the nature of YbBiPts electronic ground state.
YbBiPt is a heavy-fermion compound possessing significant short-range antiferromagnetic correlations below a temperature of $T^{textrm{*}}=0.7$ K, fragile antiferromagnetic order below $T_{rm{N}}=0.4$ K, a Kondo temperature of $T_{textrm{K}} approx1$
K, and crystalline-electric-field splitting on the order of $E/k_{textrm{B}}=1,textrm{-},10$ K. Whereas the compound has a face-centered-cubic lattice at ambient temperature, certain experimental data, particularly those from studies aimed at determining its crystalline-electric-field scheme, suggest that the lattice distorts at lower temperature. Here, we present results from high-resolution, high-energy x-ray diffraction experiments which show that, within our experimental resolution of $approx6,textrm{-},10times10^{-5}$ AA, no structural phase transition occurs between $T=1.5$ and $50$ K. In combination with results from dilatometry measurements, we further show that the compounds thermal expansion has a minimum at $approx18$ K and a region of negative thermal expansion for $9<T<18$ K. Despite diffraction patterns taken at $1.6$ K which indicate that the lattice is face-centered cubic and that the Yb resides on a crystallographic site with cubic point symmetry, we demonstrate that the linear thermal expansion may be modeled using crystalline-electric-field level schemes appropriate for Yb$^{3+}$ residing on a site with either cubic or less than cubic point symmetry.
We report on the first study of the noncentrosymmetric ternary carbide YbCoC$_{2}$. Our magnetization, specific heat, resistivity and neutron diffraction measurements consistently show that the system behaves as a heavy-fermion compound, displaying a
n amplitude-modulated magnetic structure below the Neel temperature reaching $T_{N}$ = 33 K under pressure. Such a large value, being the highest among the Yb-based systems, is explained in the light of our ab initio calculations, which show that the 4f electronic states of Yb have a dual nature -- i.e., due to their strong hybridization with the 3d states of Co, 4f states expose both localized and itinerant properties.
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