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Resultados filtrados por Publicador: Universidade Cornell

‣ Paramagnetic Meissner Effect in Superconducting Single Crystals of Ba_{1-x}K_xBiO_3

Kim, Hyun-Tak; Minami, H.; Schmidbauer, W.; Hodby, J. W.; Iyo, A.; Iga, F.; Uwe, H.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
17.239934%
The paramagnetic Meissner effect (PME) in the field cooled susceptibility has been observed in superconducting single crystals of Ba_{1-x}K_xBiO_3 using magnetometers of Quantum-Design Co.. The PME is similar to that observed in cuprates and Nb superconductors. For the Ba_{0.63}K_{0.37}BiO_3 crystal, the PME is observed in cooling process under the field up to 750 Oe. The PME was not found in the virgin-charged superconducting magnet. The PME is found in a superconductor with trapped flux and may arise from a remnant field, a temperature inhomogeneity near T_c, and a potassium-concentration inhomogeneity.; Comment: 4 pages, 4 figures

‣ Piezomagnetic effect as a counterpart of negative thermal expansion in magnetically frustrated Mn-based antiperovskite nitrides

Zemen, Jan; Gercsi, Zsolt; Sandeman, Karl G.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 10/12/2015 Português
Relevância na Pesquisa
17.239934%
The interplay of magnetic and elastic properties due to geometrical frustration in antiferromagnetic Mn-aniperovskite nitrides manifests itself in a range of phenomena such as the barocaloric (BCE), piezomagnetic (PME), magnetovolume effect (MVE), and the related negative thermal expansion (NTE). This systematic computational study uses density functional theory across a wide range of cubic antiperovskites Mn$_3$AN (A = Rh, Pd, Ag, Co, Ni, Zn, Ga, In, Sn) in order to account for variations in the magnetic frustration based on features of the electronic structure. It focuses on PME - the linear dependence of magnetisation on applied biaxial strain. The PME in Mn$_3$SnN predicted here is an order of magnitude larger than PME modelled so far in Mn$_3$GaN,\cite{lukashev2008theory} which opens the way to composite magnetoelectric effect in piezomagnetic/piezoelectric heterostructures. Moreover, the simulated PME as a zero temperature property is shown to be inversely proportional to the measured spontaneous volume expansion at a phase transition from paramagnetic (PM) to antiferromagnetic (AFM) state.\cite{takenaka2014magnetovolume} On the fundamental level, such relation implies a significant suppression of spin fluctuations by the strong frustration in these systems. At the same time it can be used as a tool in search for materials with large negative thermal expansion and barocaloric effect.; Comment: 8 pages...