|
M. Janoschek, R. E. Baumbach, J. J. Hamlin, L. Shu, I. K. Lum, D. Zocco, Jim O'Brien, P.-C. Ho, and M. B. Maple
It is well known that in materials based on elements with unstable f-electron shells, strong electronic correlations can promote new and unexpected phenomena. Here, we report results on the non-centrosymmetric family of pnictogen-based compounds Ln2M12P7 (Ln=lathanide or actinide, M=Fe,Co), that demonstrate a striking abundance of strongly correlated electron phenomena, that can be accessed by a variety of tuning parameters [1, 2, 3], and provide a new playground for probing strongly correlated electron physics.
We will discuss the unusual phase diagram in single crystals of Yb2Fe12P7, which exhibits a crossover from a zero magnetic field non-Fermi-liquid (NFL) ground state to another distinct NFL quantum region which is stabilized with magnetic field. Interestingly, the transition between the two states coincides with the suppression of magnetism towards T = 0 K at a putative quantum critical point (QCP). This scenario is fundamentally different from the "classical" QCP scenario, where NFL behavior is only observed in a narrow V-shaped region around the QCP, and we thus argue that a fundamental understanding of QCP and NFL phenomena and their interrelationship has yet to be realized.
Further, we will review measurements of the electrical resistivity, magnetization and specific heat on single crystals of Sm2Fe12P7, that exhibits itinerant ferromagnetic (FM) order below TM,1 = 6.3 K. An enhanced value for the coefficient of the electronic specific heat γ ∼ 450 mJ mol-1K-1 is observed, that is accompanied by a large coefficient A of the T2 term in the electrical resistivity, suggesting a heavy fermion (HF) ground state. Three consecutive magnetic phase transitions, indicative of competing magnetic energy scales, and the observation of a metamagnetic transition suggest proximity to a FM QCP. Thus, we propose, that Sm2Fe12P7 is a possible candidate to study FM quantum critical fluctuations in a HF compound. This represents a crucial task, since the body of work on HF systems focuses on the investigation of antiferromagnetic QCPs.
[1] R. E. Baumbach , J. J. Hamlin, L. Shu, D. A. Zocco, J. R. O'Brien, P.-C. Ho, and M. B. Maple, Phys. Rev. Lett. 105 106403 (2010) [2] M. Janoschek, R. E. Baumbach , J. J. Hamlin , I. K. Lum, M. B. Maple 2010, accepted to the special issue SCES 2010 of J. Phys.: Condens. Matter [3] R. E. Baumbach , J. J. Hamlin, M. Janoschek, I. K. Lum, M. B. Maple 2010, accepted to the special issue SCES 2010 of J. Phys.: Condens. Matter |
|