Specific heat of Nd1−xCaxB

Abstract

We measured the heat capacity on random alloys of Nd 1−x Ca x B 6 (x < 0.4) in the 0.4 to 300 K temperature range. We calculated the lattice contribution to the specific heat, arising from the Debye-type phonons of the boron framework and Einstein-type oscillators of the cation sublattice. Subtracting lattice and Schottkytype contributions from the measured heat capacity, we find that the electronic portion, linear in temperature, decreases sharply upon doping with Ca.

Defect Mode in LaB_{6}

“…1. The obtained data agrees rather well with that of [4,5] beyond the temperature interval of 4.2 20 K, where the defect-mode dominates. Other contributions to specic heat were calculated in the framework of standard procedure previously applied in [2,5].…”

“…The obtained data agrees rather well with that of [4,5] beyond the temperature interval of 4.2 20 K, where the defect-mode dominates. Other contributions to specic heat were calculated in the framework of standard procedure previously applied in [2,5]. To estimate the electronic term C el = γ · T we took the value γ ≈ 2.4 mJ/(mol·K 2 ) which is close to the results of electronic structure calculations [7] and previous specic heat analysis of LaB 6 [2,5].…”

“…Taking into account the details of RB 6 's local structure, where one boron vacancy belongs to four neighboring cells, the real vacancy concentration is determined by the relation n vac = N 2 /4 = 1.5%. Note that the defect mode contribution of LaB 6 may also be estimated from data presented in [4,5]. Moreover, the existence of TLS was experimentally detected from the recent Raman spectra investigations of LuB 12 [11], which is a nonmagnetic analog of LaB 6 .…”

“…Other contributions to specic heat were calculated in the framework of standard procedure previously applied in [2,5]. To estimate the electronic term C el = γ · T we took the value γ ≈ 2.4 mJ/(mol·K 2 ) which is close to the results of electronic structure calculations [7] and previous specic heat analysis of LaB 6 [2,5]. The phonon Let us consider the defect mode contribution to the specic heat of LaB 6 .…”

Kondo Physics in a Rare Earth Ion with Well Localized4fElectrons

“…The 4f 3 J ¼ 9=2 crystal field scheme for the full cubic site symmetry of the Nd ion has been determined by both inelastic neutron [11] and Raman scattering [12] experiments to be a ground state À 2 8 quartet, with the À 1 8 quartet and À 6 doublet lying at 135 and 278 K above the ground state, respectively. An analysis of the temperature dependent specific heat using this magnetic level scheme, in addition to the lattice specific heat of LaB 6 , led to the surprising conclusion that the electronic specific heat of NdB 6 above T N equaled 90 mJ=mole Nd K 2 [13]. This has prompted the investigation of the single ion properties of Nd dissolved in the isoelectronic, isostructural host LaB 6 reported here.…”