Sarkar R, Ghoshray A, Pahari B, Ghosh M, Ghoshray K, Bandyopadhyay B, Majumder M, Anand V K, Hossain Z
Experimental Condensed Matter Physics Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064, India.
J Phys Condens Matter. 2009 Oct 14;21(41):415602. doi: 10.1088/0953-8984/21/41/415602. Epub 2009 Sep 24.
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, ν(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, χ, plot. The calculated value of H(hf) at the (11)B ((195)Pt) is 0.156 (6.86) kOe/μ(B) in the range 30-300 K and ∼0 (0.22) kOe/μ(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 ∼T(α), with an exponent α∼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 α = 1.0, as if the behavior of the conduction electrons approaches towards a Fermi liquid, when probed near the (11)B site.
我们报道了CePt₂B₂C在4 - 315 K范围内的¹¹B和¹⁹⁵Pt核磁共振奈特位移K以及自旋 - 晶格弛豫率1/T₁。硼核的四极耦合常数ν(Q)为790 ± 10 kHz。在奈特位移K与磁化率χ的关系图中，在30 K以下观察到超精细场H(hf)的变化。在30 - 300 K范围内，¹¹B（¹⁹⁵Pt）处的H(hf)计算值为0.156（6.86）kOe/μ(B)，在30 K以下约为0（0.22）kOe/μ(B)。1/T₁与T曲线显示出一些奇异行为。通过减去从其镧类似物LaPt₂B₂C估计的T₁ᴷ⁻¹，可得到每种情况下Ce 4f自旋对核弛豫率（1/T₁f）的贡献。在¹¹B共振的情况下，在300 - 100 K的温度范围内，（1/T₁f）与T无关，表明动态磁化率虚部具有居里 - 外斯行为。然后在100 - 70 K范围内它显示出缓慢但持续的增加，表明Ce 4f自旋之间短程磁关联发展的特征。在70 K以下，1/T₁f的这种增强被完全抑制且急剧下降，表明由于近藤效应超过RKKY相互作用，磁关联效应被抑制。对于¹⁹⁵Pt，在4 - 30 K范围内以及对于¹¹B共振在8 - 30 K范围内，1/T₁f遵循Tⁱ，指数α0.7。这是非费米液体行为的一个特征。然而，在¹¹B的情况下，在8 K以下1/T₁f与T曲线的斜率再次有明显变化，α值 = 1.0，就好像当在¹¹B位点附近探测时，传导电子的行为接近费米液体。
