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11 B and 195 Pt NMR study of heavy-fermion compound CePt 2 B 2 C
R Sarkar, A Ghoshray, B Pahari, M Ghosh, K Ghoshray, B Bandyopadhyay, , V Anand K, Z Hossain
Published in
Volume: 21
Issue: 41
We report (11)B and (195)Pt NMR Knight shift K and spin-lattice relaxation rate 1/T(1) in CePt(2)B(2)C in the range 4-315 K. The quadrupolar coupling constant, nu(Q) for boron nuclei is 790 +/- 10 kHz. The change of hyperfine field, H(hf), is observed below 30 K in the K versus susceptibility, chi, plot. The calculated value of H(hf) at the (11)B ((195)Pt) is 0.156 (6.86) kOe/mu(B) in the range 30-300 K and approximately 0 (0.22) kOe/mu(B) below 30 K. The 1/T(1) versus T curve shows some exotic behavior. The Ce 4f spin contribution to the nuclear relaxation rate (1/T(1f)) in each case is obtained by subtracting the T(1K)(-1) estimated from its La analog, i.e. LaPt(2)B(2)C. In the case of (11)B resonance, in the temperature range of 300-100 K, (1/T(1f)) is independent of T, suggesting a Curie-Weiss behavior of the imaginary part of the dynamic susceptibility. It then shows a slow but continuous increment in the range 100-70 K, indicating a signature of the development of short-range magnetic correlation among the Ce 4f spins. Below 70 K, this enhancement of 1/T(1f) is completely suppressed and it decreases sharply, indicating a suppression of the effect of magnetic correlation, due to the dominance of the Kondo effect over the RKKY interaction. 1/T(1f), follows approximately T(alpha), with an exponent alpha approximately 0.7 in the range 4-30 K for (195)Pt and in the range 8-30 K for (11)B resonance. This is a characteristics of a non-Fermi-liquid like behavior. However, in the case of (11)B, there is again a clear change in the slope of the 1/T(1f) versus T curve below 8 K, with the value of alpha = 1.0, as if the behavior of the conduction electrons approaches towards a Fermi liquid, when probed near the (11)B site.
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