Electrical resistivity and thermopower of single-crystalRNi2B2C(

Anil K. Bhatnagar

¹

,

K. D. D. Rathnayaka

²

,

D. G. Naugle

³

et al.

Abstract

The in-plane resistivity and thermopower S of single crystal RNi 2 B 2 C ͑RϭDy, Ho, Er, Tm͒ has been measured from 4 to 300 K. The resistivity is linear in temperature from about 100 to 300 K, but the lowtemperature dependence goes as T p with pϭ3.0, 2.6, 2.0, and 1.4, respectively, from Dy to Tm, in comparison to the T 2 behavior previously reported for LuNi 2 B 2 C. The thermopower exhibits a region linear in T from about 100 to 300 K where the coefficient b scales by the de Gennes factor (gϪ1) 2 J(Jϩ1) for different R ϭLu, Tm-Dy. The quantity S-bT is surprisingly similar in temperature dependence and magnitude for samples with RϭY, Lu, Dy-Tm, suggesting a common, nonmagnetic contribution to the thermopower of these compounds. ͓S0163-1829͑97͒07625-X͔

Thermal transport of the single-crystal rare-earth nickel borocarbidesRNi2B2C

“…The absolute thermoelectric power of all the compounds discussed in this paper is similar in temperature dependence and close in magnitude to that reported previously by Rathnayaka et al 22 and Bhatnagar et al 23 for other single-crystal samples of these materials. The high temperature (T у100 K) S for RϭY and Lu-Dy is approximately linear in temperature dependence and is negative for the entire temperature range.…”

“…Figure 7 shows the a-b plane absolute thermopower versus temperature for the first ErNi 2 B 2 C sample from 1.5 to 300 K. The temperature dependence of the high temperature S shown for this sample is typical of all of the members of the RNi 2 B 2 C family discussed in this paper, except for RϭTb and Gd. An analysis of the thermoelectric power ͑see Hennings 4 for detailed discussion͒ that was somewhat similar to that performed earlier by Bhatnagar et al, 23 indicates that the presence of disordered magnetic spins adds a term linear in temperature and proportional to the de Gennes factor of the trivalent rare-earth ions to the high-temperature thermoelectric power. This conclusion is in agreement with the general results reported earlier by Gratz and Zuckermann 19 for rare-earth transition-metal compounds.…”

“…The high temperature (T у100 K) S for RϭY and Lu-Dy is approximately linear in temperature dependence and is negative for the entire temperature range. Each of these materials also has a quite large ͑negative 2-6 V/K͒ intercept when the linear portion is extrapolated down to T ϭ0 K. This behavior in S is quite anomalous as discussed earlier, 22,23 as is the high temperature thermal conductivity. The room temperature S's range from 7 to 14 V/K.…”

“…The presence of disordered magnetic spins has been found to add a term linear in temperature and proportional to the de Gennes factor to the high temperature thermo-electric power consistent with the work of others. 1,19,23 There is also a low temperature enhancement in the magnitude of the thermoelectric power that is not masked by superconductivity for the three samples that have antiferromagnetic order above T c . The magnetic moments are responsible for interesting effects in the low-temperature thermal conductivity such as the gapless superconductivity in HoNi 2 B 2 C. The sharp increase in the thermal conductivity of TmNi 2 B 2 C at Tϭ1.4 K is probably due to additional heat conduction by magnons.…”

Physical properties of Lu1−xYbxNi2B2C

“…The additional contribution a is large and temperature independent above 100 K; it rapidly goes to zero below 100 K and does not show evidence of a phonon-drag 'peak'. Similar behaviour was observed in all of the other superconducting rare earth nickel borocarbides (R ¼ Tm, Er, Ho, Dy, Y, and Lu), with a value of b that is roughly the same for all R [38]. In contrast, S is non-linear for x > 0 over the entire measured temperature range, which suggests additional strongly temperature dependent terms are dominant.…”