La substitution effect and hyperfine-enhancedP141rnuclear spin dynamics inPrPb3

Abstract

La NMR studies have been performed on PrPb 3 substituted with 3% La. The temperature dependence of the local magnetic susceptibility around La ions has been extracted from the 139 La Knight shift. These data show that the nonmagnetic ⌫ 3 crystalline-electric-field ͑CEF͒ ground state ͑GS͒ is preserved even at the nearest neighboring Pr ions, although their CEF level scheme is slightly modified due to the La substitution. On the other hand, the temperature dependence of the nuclear spin-lattice relaxation rate 1 / T 1 is found to be well reproduced by assuming the same CEF level scheme over a wide temperature range. However, 1 / T 1 shows a strong upturn below 10 K, which is not expected from the nonmagnetic CEF GS. We show that the lowtemperature anomaly can be quantitatively understood in terms of a cross-relaxation process between 141 Pr and 139 La nuclear spins. Analysis of the cross-relaxation process reveals strong nuclear spin-spin coupling among the 141 Pr nuclei, which we suggest is enhanced by a hyperfine mechanism of Pr ions and then mediated by relatively large indirect magnetic coupling between them.

Magnetic excitations andc-fhybridization effect in PrTi2Al20Tokunaga1, Sakai2, Kambe3 et al. 2013Phys. Rev. B404230View full textAdd to dashboardCite

“…Indeed, a similar temperature behavior has also been observed in other Pr compounds having a nonmagnetic CEF ground state, such as PrAg 2 In, 14 PrMg 3 , 15 and Pr 0.97 La 0.03 Pb 3 . 16 However, there is a small but significant difference in 1/T 1 behavior; that is, there is a broad humplike feature peaking around 70-100 K in both PrTi 2 Al 20 and PrV 2 Al 20 which is not observed in the other Pr compounds. This characteristic feature is important, because it is related to the strong c-f hybridization effect in the present systems, as is discussed below.…”

“…2. 16 On the other hand, the CEF level scheme for PrV 2 Al 20 has not been established up to now. We therefore deduce this level scheme for our analysis below by fitting the temperature dependence of K(T ).…”

“…17,18 Indeed, the calculations of (1/T 1 ) f for PrAg 2 In, 14 PrMg 3 , 15 and Pl 0.97 La 0.03 Pb 3 (Ref. 16) have been made with this assumption, using a similar formula to Eq. (2), and succeeded in reproducing the temperature variation over a wide range (except at very low temperatures).…”

“…3,7 Pr ions are surrounded by 16 Al ions, forming the so-called Frank-Kasper cage. 8 Because of this large coordination number, a strong hybridization between 4f and conduction electrons is expected.…”

Perturbation on hyperfine-enhancedPr141nuclear spin dynamics associated with antiferroquadrupolar order inPrV2Al20Ito1, Higemoto2, Sakai3 et al. 2015Phys. Rev. B8030View full textAdd to dashboardCite

“…The MHz-scale ν is typical of exchangemediated 141 Pr nuclear spin-spin interactions in nonmagnetic CEF ground states [10,14,21,[24][25][26], further justifying our model. A marked reduction in ν at 0.045 K clarifies that the step-like increase in 1/T 1,µ below 1 K in ZF is mainly due to the slowing down of 141 Pr nuclear spin fluctuations.…”