Low temperature heat capacities of DyConi

Heat capacity data are presented for DyCoNi in the temperature range 4.2 to 300 K. The sample exhibits an anomaly peaking at 63 K. This is interpreted as arising from ferromagnetic ordering. Resistivity measurements also indicate an anomaly at 63 K. The magnetic entropy, evaluated by using the heat capacity data of LaNi₂ as “a blank” ins nearly R in 4. These results are interpreted on the basis of an accidental four-fold degeneracy of the ground state of the Dy³⁺. The itinerant nature of the cobalt moment proposed by Taylor et al. appears to be valid in this compound.     

Low temperature heat capacities of transition metal phosphidest2

Low temperature heat capacities of transition metal phosphides, T₃P, (T = transition metal) are characterized by large γ values which indicate the existence of a narrow d-band in these materials. Anomalous γ values are observed at compositions close to the onset of a long range magnetic state.     

Low temperature thermal properties of PbI2

The heat capacity and thermal conductivity of a large (56.5 g) crystal of PbI₂ have been measured in the temperature region 0.5 < T < 3.9°K. Analysis of the heat capacity data yields a value of the limiting apparent Debye characteristic temperature θ₀^c = 99.4 (±0.3)°K, which corresponds to an average lattice wave velocity of 1.151 (±0.005) × 10⁵ cm sec^?1. It is consistent with a wave velocity estimated from neutron scattering experiments, but not with one determined from Brillouin spectra. The heat capacity data also show that dispersion of the low frequency waves is not unusual, as might have been expected for a layer-type crystal. The apparent thermal conduction is found to be surprisingly small in the crystal.     

Low temperature thermal properties and intrinsic defects in vitreous silica

Measurements of the low temperature specific heatC _p (0.04KT2.4K) and thermal conductivityk (0.5KT20K) of high purity vitreous silica (Suprasil W) in the as-received and electron-irradiated states are reported. In the temperature range where the localized excitations inherent in glasses dominateC _p (T0.5K) no change is observed upon electron irradiation of up to 10¹⁹e^– (total dose). An anomalyC around 1.8K is observed inC _p which is reduced by 40% upon irradiation. However, ask is not affected by electron irradiation, localized excitations as origin forC can be ruled out. The density of paramagnetic centers in the most heavily irradiated sample is 510¹⁷cm^–3 as obtained from the ESR signal. It has been suggested that these centers have diamagnetic precursors in the unirradiated glass. Our measurements indicate that those defects are not associated with the localized excitations.     

Low temperature thermal—and magnetic properties of CeP and CeAs

CeP and CeAs are characterized by low temperature measurements of the specific heat, the thermal expansion, the electrical resistivity and the magnetization of single crystal specimens. These physical properties are found to be very sensitive to crystal perfection and chemical composition in both the paramagnetic and the magnetically ordered state. In the intrinsically antiferromagnetic CeP, imperfections can give rise to a remanent magnetization belowT _N .     

Low temperature thermal properties of mixed crystal KBrKI

The low temperature specific heat and thermal conductivity of KBr_0.53I_0.47 mixed crystal are measured. This material is known to have compositional fluctuations on a scale of order 1000 Å. The thermal properties, however, are well described by the Debye model and show no indication of glass-like thermal behavior.     

Low temperature thermal properties of crystalline quartz after electron irradiation

Measurements of the temperature specific heat (between 0.12K and 8K) and thermal conductivity (between 0.5K and 20K) of crystalline -quartz after electron irradiation are reported. In the temperature region below 1K the specific heat is larger than in the unirradiated sample. This can be attributed to low energy excitations which are created during irradiation and which are associated with Al impurities. The thermal conductivity is reduced after irradiation. Below 4K the additional thermal resistivity varies asT ^–1.5. The phonon scattering by radiation-induced excitations in -quartz is weak compared to phonon scattering by two level systems (TLS) in vitreous silica.     

Low temperature magnetic properties of NdCu2

μSR experiments on NdCu₂ give evidence for short range order below 25\ K above T_N=6.5\ K. No signal was detected between 16\ K and 1.2\ K where neutron scattering reveals an incommensurate spin structure. Below 1.2\ K the μSR signal is recovered and shows a rotation with 22 MHz. This is interpreted with a squaring up of Nd spins accompanied by a decrease of magnon excitations which is reflected in a decrease of damping of the muon signal. This revised version was published online in July 2006 with corrections to the Cover Date.     

Low temperature thermal magnetoresistance of potassium

Unexpected magnet field behavior is observed in the low temperature thermal magnetoresistance of potassium. The thermal resistance does not saturate nor does it mirror the electrical magnetoresistivity. At high fields, a field dependent Wiedemann-Franz ratio is observed.     

Low temperature thermal magnetoconductance of metals

A low temperature transverse thermal magnetoconductance of metals and semimetals is treated theoretically. It is shown that its high magnetic field behavior is determined by the characteristic time τ_ɛ of jumps from one cyclotron circle to another due to electron-phonon collisions rather than by the transport time τ_tr that determines the conductance. The phonon-electron drag contribution to the magnetoconductance is also discussed.     

Low temperature specific heat of ErAs

The specific heat of a sintered sample of ErAs has been measured from 1.4–6.1 K. A single broad κ-like peak in the data occurs at 3.25K. The entropy associated with the peak is approximately R ln4 suggesting an $\text{S′ =}\text{3}\text{2}$ ground state.     

Low temperature heat capacity of YBa2Cu3O7

We have measured the heat capacity of superconducting, single phase YBa₂Cu₃O₇ in the temperature range 2 to 18 K. An extrapolation of the data between 4 and 9 K gives aC/T (T → 0) of ∼ 25 mJ/mole K². The Debye temperature obtained from the high temperature linear portion ofC/T vsT ² plot is 325 K.     

Low temperature thermal expansion and magnetostriction of TmCd

Thermal expansion measurements in various external magnetic fields confirm the recently found Jahn-Teller transition in TmCd at 3.16 K. The tetragonal strain ?₃ at T = 0 K is found to be 0.62 × 10^?3. From magnetostriction data we determine a coupling constant g₀² = 0.4 × 10^?3 K which is in good agreement with the value found from ultrasonic experiments. In order to explain our magnetostriction results in the cubic phase, g₀ has to be taken negative.     

Pressure and temperature induced structural,electronic and thermal properties of CdAl2Se4

We present a comprehensive computational study on the ground state properties of CdAl₂Se₄; a defect chalcopyrite compound. Considering its potential application, we have calculated the electronic band structures using the full potential linear augmented plane wave method within the density functional theory at ambient conditions and higher pressure and temperatures. The obtained Density of states at ambient conditions compares favourably with the available experimental and theoretical results. Our calculated band gap is in excellent agreement with experimental results. Thermal effects are obtained employing quasi-harmonic Debye model. The changes in properties associated with the electronic structure of CdAl₂Se₄ are evaluated at various temperatures and pressures.     

Low temperature specific heat of Cr-Fe-Si alloys

Low temperature specific heats of Cr-Fe-Si alloys with 3 at. % Si were investigated between 1.4°–4.2°K. The electronic specific heat coefficient γ essentially varies with transition metal electron concentration ( e/a) in the same manner as the Cr-Fe alloys but with the high γ peak slightly shifted to lower e/a. The shift of γ peak suggests transfer of electrons from Si atoms to the 3d magnetic subband of the transition elements.     

Low temperature heat capacity of Rh-Cu alloys

Reported here are the low temperature heat capacity data on a series of single phase fcc Rh-Cu alloys. The electronic heat capacity coefficient, γ, decreases rapidly up to 20 at % of copper in Rh and then stays constant to ～60 at % Cu after which decreases smoothly to the pure Cu value. This is interpreted as due to the initial partial filling of the d-band after which the conduction electron of Cu goes into the s-band. An attempt is made to understand the origins of the curious anomalies in the Debye temperature and microhardness data.     

Low temperature heat capacity of electrotransported scandium

The heat capacity of two scandium samples containing 1.6 and <5 ppm atomic Fe was measured from 1 to 20 K. The weighted values for γ and θ_D are: 10.340 ± 0.018 mJ/g-at. K² and 346.1 ± 0.9 K, respectively. This is the first time anyone has obtained the same heat capacity results on two different scandium samples. The iron impurity concentration appears to be critical.