Magnetic Field–Temperature Phase Diagram of Fine YBa2Cu3O7−δ Ceramics from Linear and Non-linear Resistivities

We performed linear and non-linear resistivity measurements for fine YBa2Cu3O7−δ ceramics under magnetic field. Successive superconducting transition was observed in the linear resistivity and the lower temperature part of the resistivity curve became convex upward at high fields. A non-linear resistivity peak was observed for this lower temperature region and its offset temperature Toffset and the onset temperature Tonest coincided with the temperature of zero resistivity and inflexion point in linear resistivity, respectively. At lower field, Tonset was less sensitive to the field than Toffset, which implies the existence of the peculiar inter-grain ordering phase at finite fields.2019 International Conference on Strongly Correlated Electron Systems (SCES2019), September 23-28, 2019, Okayama Convention Center in Okayama, Japa

Oxidation and reduction effects of successive superconducting transitions in ultra-fine YBa2Cu4O8 ceramics

We investigated the effects of oxidation and reduction on the successive superconducting transition in a ceramic material composed of YBa2Cu4O8 (Y124) submicron grains by linear and non-linear resistivity measurements. This material shows two-step superconducting transition and the lower one is identified as an inter-grain ordering. A sintering process fuses and joins the adjacent grains, so the lower transition was suppressed with increasing sintered time. Although Y124 is a stoichiometric ceramic, a reduction treatment suppressed the temperature of zero resistivity and broadened the non-linear resistivity peak. This suggests an oxygen vacancy was induced on the grain surface

NMR study of the layered cobalt oxyphosphide Sr2Sc(Co1-xFex)PO3

We report the results of 31P-nuclear magnetic resonance (NMR) measurements on the layered cobalt oxyphosphide Sr2Sc(Co1−xFex)PO3 in order to investigate the magnetic properties at low temperatures from a microscopic view point. The 31P-Knight shifts measured at the resonance peak maximum of Sr2Sc(Co1−xFex)PO3 have positive values and are T-independent in an entire temperature range, and the absolute value decreases with increasing Fe content. Also, the nuclear spin-lattice relaxation rate 1/T1 is almost proportional to the temperature at low temperatures. The magnitude of 1/T1T decreases with increasing the Fe content, which suggests the decrease of the density of states around the Fermi level

Magnetic Field–Temperature Phase Diagram of Fine YBa2Cu3O7−δ Ceramics from Linear and Non-linear Resistivities

We performed linear and non-linear resistivity measurements for fine YBa2Cu3O7−δ ceramics under magnetic field. Successive superconducting transition was observed in the linear resistivity and the lower temperature part of the resistivity curve became convex upward at high fields. A non-linear resistivity peak was observed for this lower temperature region and its offset temperature Toffset and the onset temperature Tonest coincided with the temperature of zero resistivity and inflexion point in linear resistivity, respectively. At lower field, Tonset was less sensitive to the field than Toffset, which implies the existence of the peculiar inter-grain ordering phase at finite fields.2019 International Conference on Strongly Correlated Electron Systems (SCES2019), September 23-28, 2019, Okayama Convention Center in Okayama, Japa