https://doi.org/10.1140/epjb/e2006-00043-y
Lower critical field and intragrain critical current density in the ruthenate-cuprate RuSr2Gd1.5Ce0.5Cu2O10
1
Instituto de Física, Universidade Federal do Rio de Janeiro, C.P. 68528, RJ, 21941-972, Brazil
2
Instituto de Física, Universidade Federal Fluminense, Niterói, RJ, 24210-340, Brazil
3
Laboratorio de Superconductividad, Facultad de Física-IMRE, Universidad de La Habana, San Lázaro y L, Ciudad de La Habana, 10400, Cuba
Corresponding author: a sgg@if.ufrj.br
Received:
19
August
2005
Revised:
16
November
2005
Published online:
17
February
2006
The lower critical field of the grains, Hc1, and the intragrain
critical current density, Jc, were determined for the superconducting
ruthenate-cuprate RuSr2Gd1.5Ce0.5Cu2O10-δ
[Ru-1222(Gd)] through a systematic study of the hysteresis in
magnetoresistance loops. A reliable method, based on the effects of the
magnetization of the grains on the net local field at the intergranular
junctions is provided, circumventing the problem of the strong masking of
the superconducting diamagnetic signal by the ferromagnetic background. The
temperature dependency of Hc1 and Jc both exhibit a smooth
increase on cooling without saturation down to 
. The
obtained Hc1 values vary between 150 and 1500 Oe in the 0.2 ≤
T/TSC ≤0.4 interval, for samples annealed in an oxygen flow;
oxygenation under high pressure (50 atm) leads to a further increase. These
values are much larger than the previously reported rough assessments (25–50
Oe), using conventional magnetization measurements. High Jc values of
~107 A/cm2, comparable to the high-Tc cuprates, were
obtained. The Hc1(T) and Jc(T) dependencies are explained in the
context of a magnetic phase separation scenario.
PACS: 74.72.-h – Cuprate superconductors (high-Tc and insulating parent compounds) / 74.25.Fy – Transport properties (electric and thermal conductivity, thermoelectric effects, etc.) / 74.25.Ha – Magnetic properties
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2006
