279 research outputs found
Superconductivity in the Correlated Pyrochlore Cd_2Re_2O_7
We report the observation of superconductivity in high-quality
CdReO single crystals with room-temperature pyrochlore structure.
Resistivity and ac susceptibility measurements establish an onset transition
temperature T = 1.47 K with transition width T = 0.25
K. In applied magnetic field, the resistive transition shows a type-II
character, with an approximately linear temperature-dependence of the upper
critical field H. The bulk nature of the superconductivity is confirmed
by the specific heat jump with C = 37.9 mJ/mol-K. Using the
value extracted from normal-state specific heat data, we obtain
C/T = 1.29, close to the weak coupling BCS value. In the
normal state, a negative Hall coefficient below 100 K suggests electron-like
conduction in this material. The resistivity exhibits a quadratic T-dependence
between 2 and 60 K, i.e., +AT, indicative of Fermi-liquid
behavior. The values of the Kadowaki-Woods ratio A/ and the Wilson
ratio are comparable to that for strongly correlated materials.Comment: 4 pages, 5 figure
Design and development of the Australian and New Zealand (ANZ) myeloma and related diseases registry
© 2016 The Author(s). Background: Plasma cell dyscrasias (PCD) are a spectrum of disorders resulting from the clonal expansion of plasma cells, ranging from the pre-malignant condition monoclonal gammopathy of undetermined significance (MGUS) to multiple myeloma (MM). MM generates a significant burden of disease on the community and it is predicted that it will increase in both incidence and prevalence owing to an ageing population and longer survival secondary to new therapeutic options. Robust and comprehensive clinical data are currently lacking but are required to define current diagnostic, investigational and management patterns in Australia and New Zealand (ANZ) for comparison to both local and international guidelines for standards of care. A clinical registry can provide this information and subsequently support development of strategies to address any differences, including providing a platform for clinical trials. The Myeloma and Related Diseases Registry (MRDR) was developed to monitor and explore variations in practices, processes and outcomes in ANZ and provide benchmark outcomes nationally and internationally for PCD. This paper describes the MRDR aims, development and implementation and discusses challenges encountered in the process. Methods: The MRDR was established in 2012 as an online database for a multi-centre collaboration across ANZ, collecting prospective data on patients with a diagnosis of MGUS, MM, solitary plasmacytoma or plasma cell leukaemia. Development of the MRDR required multi-disciplinary team participation, IT and biostatistical support as well as financial resources. Results: More than 1250 patients have been enrolled at 23 sites to date. Here we describe how database development, data entry and securing ethics approval have been major challenges for participating sites and the coordinating centre, and our approaches to resolving them. Now established, the MRDR will provide clinically relevant and credible monitoring, therapy and 'real world' outcome data, to support the conduction of high quality studies. In addition, the Myeloma 1000 sub-study is establishing a repository of paired peripheral blood specimens from registry patients to study mechanisms underlying disease progression. Conclusion: Establishment of the MRDR has been challenging, but it is a valuable investment that will provide a platform for coordinated national and international collaboration for clinical research in PCD in ANZ
Renal impairment at diagnosis in myeloma: Patient characteristics, treatment, and impact on outcomes. Results trom the Australia and New Zealand myeloma and related diseases registry
Background: Renal impairment (RI) is a common complication of multiple myeloma (MM) and remains a poor prognostic factor despite improved survival with newer therapies. Patients and Methods: We evaluated baseline characteristics, treatment, and outcomes of newly diagnosed MM patients with RI at diagnosis in the Australia and New Zealand Myeloma and Related Diseases Registry over 5 years to April 2018; we compared patients with RI (estimated glomerular filtration rate [eGFR
Magnetic and charge transport properties of the Na-based Os oxide pyrochlore
Na-based osmium oxide pyrochlore was synthesized for the first time by an
ion-exchange method. KOs2O6 was used as a host compound. Elelectron probe
micro-analysis, synchrotron x-ray diffraction analysis, and thermo-gravimetric
analysis confirmed its structure not as the beta-type but as the defect-type
pyrochlore. The composition was identified as Na1.4Os2O6.H2O. Electrical
resistivity, heat capacity, and magnetization measurements of the
polycrystalline Na1.4Os2O6.H2O clarified absence of superconductivity above 2
K, being in contrast to what were found for the beta-pyrochlore AOs2O6 (A = Cs,
Rb, K). Sommerfeld coefficient of 22 mJ K-2 mol-1 of Na1.4Os2O6.H2O was
smallest among those of AOs2O6. A magnetic anomaly at ~57 K and possible
associated magnetoresistance (+3.7 % at 2 K in 70 kOe) were found.Comment: 19 pages, 6 figures, Submitted to PR
Superconductivity at 1 K in Cd2Re2O7
We report the first pyrochlore oxide superconductor Cd2Re2O7.
Resistivity,magnetic susceptibility,and specific heat measurements on single
crystals evidence a bulk superconductivity at 1 K. Another phase transition
found at 200 K suggests that a peculiar electronic structure lies behind the
superconductivity.Comment: 4 pages, 4 figures, PRL, in pres
Coexistence of metallic and nonmetallic properties in the pyrochlore Lu2Rh2O7
Transition metal oxides of the and block have recently become the
targets of materials discovery, largely due to their strong spin-orbit coupling
that can generate exotic magnetic and electronic states. Here we report the
high pressure synthesis of LuRhO, a new cubic pyrochlore oxide
based on Rh and characterizations via thermodynamic, electrical
transport, and muon spin relaxation measurements. Magnetic susceptibility
measurements reveal a large temperature-independent Pauli paramagnetic
contribution, while heat capacity shows an enhanced Sommerfeld coefficient,
= 21.8(1) mJ/mol-Rh K. Muon spin relaxation measurements confirm
that LuRhO remains paramagnetic down to 2 K. Taken in combination,
these three measurements suggest that LuRhO is a correlated
paramagnetic metal with a Wilson ratio of . However, electric
transport measurements present a striking contradiction as the resistivity of
LuRhO is observed to monotonically increase with decreasing
temperature, indicative of a nonmetallic state. Furthermore, although the
magnitude of the resistivity is that of a semiconductor, the temperature
dependence does not obey any conventional form. Thus, we propose that
LuRhO may belong to the same novel class of non-Fermi liquids as
the nonmetallic metal FeCrAs.Comment: 11 pages, 5 figure
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