Derr J, Knebel G, Lapertot G, Salce B, Méasson M-A, Flouquet J
Département de Recherche Fondamentale sur la Matière Condensée, CEA Grenoble, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France.
J Phys Condens Matter. 2006 Feb 15;18(6):2089-106. doi: 10.1088/0953-8984/18/6/021. Epub 2006 Jan 27.
The intermediate valence systems TmSe and SmB(6) have been investigated up to 16 and 18 GPa by ac microcalorimetry with a pressure (p) tuning realized in situ at low temperature. For TmSe, the transition from an antiferromagnetic insulator for p<3 GPa to an antiferromagnetic metal at higher pressure has been confirmed. A drastic change in the p variation of the Néel temperature (T(N)) is observed at 3 GPa. In the metallic phase (p>3 GPa), T(N) is found to increase linearly with p. A similar linear p increase of T(N) is observed for the quasitrivalent compound TmS, which is at ambient pressure equivalent to TmSe at p∼7 GPa. In the case of SmB(6) long range magnetism has been detected above p∼8 GPa, i.e. at a pressure slightly higher than the pressure of the insulator to metal transition. However a homogeneous magnetic phase occurs only above 10 GPa. The magnetic and electronic properties are related to the renormalization of the 4f wavefunction either to the divalent or the trivalent configurations. As observed in SmS, long range magnetism in SmB(6) occurs already far below the pressure where a trivalent Sm(3+) state will be reached. It seems possible to describe roughly the physical properties of the intermediate valence equilibrium by assuming formulae for the Kondo lattice temperature depending on the valence configuration. Comparison is also made with the appearance of long range magnetism in cerium and ytterbium heavy fermion compounds.
通过交流微量热法，在低温下原位实现压力（p）调节，对中间价态体系TmSe和SmB₆进行了高达16 GPa和18 GPa的研究。对于TmSe，已证实其从p < 3 GPa时的反铁磁绝缘体转变为高压下的反铁磁金属。在3 GPa时观察到奈尔温度（Tₙ）的p变化发生了急剧变化。在金属相（p > 3 GPa）中，发现Tₙ随p线性增加。对于准三价化合物TmS，也观察到Tₙ随p呈类似的线性增加，在环境压力下，TmS相当于p ∼ 7 GPa时的TmSe。对于SmB₆，在p ∼ 8 GPa以上检测到了长程磁性，即压力略高于绝缘体到金属转变的压力。然而，仅在10 GPa以上才出现均匀磁相。磁性和电子性质与4f波函数重整化为二价或三价构型有关。正如在SmS中观察到的那样，SmB₆中的长程磁性在远低于达到三价Sm³⁺态的压力时就已出现。通过假设取决于价态构型的近藤晶格温度公式，似乎可以大致描述中间价态平衡的物理性质。还与铈和镱重费米子化合物中长程磁性的出现进行了比较。
