The super-heavy-fermion compound YbBiPt has the largest known linear specific-heat coe5cient y =8 Jmol ' K, and the source of this enormous "electronic" specific heat is of great current interest.Here we describe neutron-diffraction studies that indicate its previously reported crystallographic structure to be incorrect. %'e find that the Pt atom is on the unique site and can be thought of as an interstitial in a fictitious rock-salt structure YbBi, which can in turn be thought of as an ordered form of elemental bismuth. %'e find no evidence of disorder between sites, occupancy on the nominally vacant site, nor for any tetragonal or rhombohedral distortions or displacements. Furthermore, any ordered magnetic moment at low temperature must be less than 0.25pz. The sample contains 8.1 wt. %%u oelementa 1 Bi, and if this is typical of other samples, the previously published values for molar susceptibilities and specific heats should be scaled up by this amount to obtain the intrinsic properties of YbBiPt alone.The cubic heavy-fermion compound YbBiPt was discovered in 1991 by CanfMld and co-workers' and has a very large linear specific-heat coefficient y = 8 Jmol 'K 2, an order of magnitude more than that of typical heavy-fermion compounds and three orders of magnitude larger than that of conventional metals. YbBiPt forms in the C lb or MgAgAs structure type (space group E43trt), which is a common Heusler-alloy structure, and in which some uranium-based ternaries such as the UNiSn form. There is only one formula unit per primitive unit cell. It is well known that the conventional face-centered-cubic unit cell is not the primitive cell, and typically the simpler primitive rhombohedral cell is employed. The atoms are then distributed on three of the four sites along the [111] long diagonal of the rhombohedra1 ce11 is 1isted in Table I. All four sites have tetrahedral point-group symmetry 43m, but the sequence is not arbitrary in the sense that, if three sites are occupied, one can be thought of as an ordered vacancy, two of the sites have this vacancy as a nearest neighbor, and the fourth site is unique, in that it has no vacant neighbor sites. A previous x-ray study reported that Bi was on the unique site, and to date two band-structure calculations7's have assumed this sequence.In this paper, we describe the results of neutron and xray powder-difFraction studies. For these elements the neutron-diffraction contrast is approximately twice that of x rays and opposite in sign. We find that Pt actually occupies the special site rather than Bi. In addition, we address a number of other questions. Firstly, the @SR response is reminiscent of spin-glass behavior, and it has been suggested that this might be due to nonzero occupancy on the nominally vacant site, or to disorder on the occupied sites. We Snd no evidence for either. Secondly, there is evidence from inelastic neutron-scattering studies' '" of the crystal-Geld excitations that the cubic symmetry is broken. We Snd no evidence for this at room temperature, nor at 0.4...

Heavy-fermion behavior of UT2X2 compoundsHavela, L.; Sechovsky, V.; Svoboda, P.; Divis, M.; Nakotte, H.; Prokes, K.; de Boer, F.R.; Purwanto, A.; Robinson, R.A.; Seret, A.; Winand, J.M.; Rebizant, J.; Spirlet, J.C.; Richter, M.; Eschrig, H. Published in:Journal of Applied Physics DOI:10.1063/1.358314 Link to publication Citation for published version (APA):Havela, L., Sechovsky, V., Svoboda, P., Divis, M., Nakotte, H., Prokes, K., ... Eschrig, H. (1994). Heavy-fermion behavior of UT2X2 compounds. Journal of Applied Physics, 76, 6214-6216. DOI: 10.1063/1.358314 General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Magnetic and specific-heat studies of U,T& compounds show a frequent occurrence of the y enhancement in conjunction with the onset of antiferromagnetic ordering. The largest value of 830 mJ/mol K2 was observed in U,Pt,In, which is nonmagnetic down to 1.2 K. Variations of electronic structure are documented by optimized relativistic LCAO calculation.

A multiple-state quantum Carnot engine based on single particle in one dimensional potential well is evaluated. The general forms of adiabatic and isothermal force as well as work are given. We apply them first to the simplest case of two-state system, and then to three-state and general n-state system. The first isothermal expansion starts from single ground state and cease to single highest state. In Addition to the simplest case, isothermal expansions may terminate not to highest state but an intermediate state but with the same of the total expansion. The result is that the efficiency of the multi-state machine could be enhanced by reducing the volume of isothermal expansion for the same of the total volume expansion

We study the structure of CP violating phases in the seesaw model. We find that the 3ϫ6 MNS matrix contains six independent phases, three of which are identified as a Dirac phase and two Majorana phases in the light neutrino sector while the remaining three arise from the mixing of the light neutrinos and heavy neutrinos. We show how to determine these phases from physical observables.