Low Temperature Properties of the Cubic Kondo Lattice Systems SmTr₂Al₂₀(Tr= Ti, V, Cr)

Abstract

Low temperature properties of the cubic Kondo lattice systems SmT r 2 Al 20 (T r = Ti, V, Cr) Akito Sakai and Satoru NakatsujiInstitute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan. (Received November 15, 2011) We investigate the low temperature physical properties of SmT r 2 Al 20 (T r = Ti, V, Cr), namely, the specific heat C(T ) and the electrical resistivity ρ(T ). A sharp lambda like anomaly in C(T ) and drop in ρ(T ) due to an antiferromagnetic order are observed at T N = 6.4 K (Ti), 2.9 K (V), 1.8 K (Cr). Systematic change in the Sommerfeld coefficient γ and the slope of − ln T dependence of ρ with the substitution of T r reveals c − f hybridization becomes enhanced in the sequence from T r = Ti, V, Cr and suppresses the T N .

Thermoelectric Property of SmT2Al20 (T = Ti, V, and Cr) at Low Temperatures

“…In fact,  4f for T = V shows a hump centering 15 K on the simple logarithmic T dependence [7]. This anomaly seems similar with that observed for T = Ti [7], and apparently corresponds to the negative S hump.…”

“…First, we examined the reproducibility in the T dependence of  above 2 K and specific heat C below 20 K down to 0.5 K for SmT 2 Al 20 . For both quantities, we obtained properties quite similar to those for single crystals [1,6,7]. T for T = Ti exhibits a clear -ln T behavior below 60 K and a sharp drop below 7 K. C(T) exhibits a sharp peak at 6.5 K. The Sm-molar entropy at T N attains about R ln 4.…”

“…Furthermore, we can greatly expect that the Kondo effect also acts on the  7 doublet, and reflects in . We notice that the positive peak in S has a depression around 70 K. It is pointed out that  4f deviates from a logarithmic T dependence with a fold at about 80 K [7]. They seem identical in origin that is unknown for the moment.…”

“…Regarding a positive peak at 120 K in S for T = Ti as that of IV compounds, T K is evaluated as the T exceeding 150 K, whereas the peak amplitude is small. Sakai and Nakatsuji obtained the moderately high T K ~ 20 K from their  4f analysis [6,7], but noted that this may be quantitatively incorrect because they considered the case not for the realistic  8 quartet ground state but for a doublet for the experimental result. On the other hand, the S peak should be explained by the presence of the CEF with the Kondo effect, if we treat SmT 2 Al 20 as a system like the Ce-based AFM Kondo compound.…”

“…Thereafter, properties of SmT 2 Al 20 for T = V and Cr have been newly investigated [6].  for the each compound also shows a -ln T behavior, whereas it is less clear than that of SmTi 2 Al 20 [6,7]. In addition, the sommerfeld coefficient is large (150 mJ/(mol K 2 ) for Ti, 720 mJ/(mol K 2 ) for V and 1000 mJ/(mol K 2 ) for Cr), being categorized as the heavy electron (HE) system.…”