TY - JOUR
T1 - Spontaneous Vortex Phase and the Meissner-State in the Magneto- Superconductor Eu1.5Ce0.5RuSr2Cu2O 10-σ (Eu-2122)
AU - Felner, I.
AU - Sonin, E. B.
AU - Machi, T.
AU - Koshizuka, N.
PY - 2000
Y1 - 2000
N2 - The superconducting ceramic material R1.5Ce0.5RuSr2Cu2O 10-σ (Eu-2122) is also weak-ferro-magnetically ordered at TM ≫ Tc (Tc=32 and TM ∼ 122 K), thus, superconductivity (SC) coexists with ferromagnetism. SC is confined to the CuO2 planes, whereas the weak-ferromagnetic (WFM) state is due to the Ru sublattice. The observed saturation moment of the Ru sublattice is about 0.7μB per unit cell, which is translated into an internal field Bint= 4πM (higher than Hc1) of a few hundreds of G. This Bint induces vortices in the superconducting planes which have been observed in a ceramic material for the first time by means of magneto-optical imaging. Below Tc, at zero applied field, magnetic flux (the mixed state) is present in the sample in equilibrium and disappear above Tc. On the other hand, under an external field of 50 Oe, the flux density persists up to TM. These measurements confirm our predicted spontaneous vortex phase (SVP) model, which assumes that in WFM-SC materials vortices are present in the sample in equilibrium without an external field. We also show the existence of the Meissner state in the WFM-SC Eu-2122 system in which Ru is substituted by Nb. The reduced Ru moment, and as a result the weak SVP, do not mask the expulsion of the flux lines at Tc.
AB - The superconducting ceramic material R1.5Ce0.5RuSr2Cu2O 10-σ (Eu-2122) is also weak-ferro-magnetically ordered at TM ≫ Tc (Tc=32 and TM ∼ 122 K), thus, superconductivity (SC) coexists with ferromagnetism. SC is confined to the CuO2 planes, whereas the weak-ferromagnetic (WFM) state is due to the Ru sublattice. The observed saturation moment of the Ru sublattice is about 0.7μB per unit cell, which is translated into an internal field Bint= 4πM (higher than Hc1) of a few hundreds of G. This Bint induces vortices in the superconducting planes which have been observed in a ceramic material for the first time by means of magneto-optical imaging. Below Tc, at zero applied field, magnetic flux (the mixed state) is present in the sample in equilibrium and disappear above Tc. On the other hand, under an external field of 50 Oe, the flux density persists up to TM. These measurements confirm our predicted spontaneous vortex phase (SVP) model, which assumes that in WFM-SC materials vortices are present in the sample in equilibrium without an external field. We also show the existence of the Meissner state in the WFM-SC Eu-2122 system in which Ru is substituted by Nb. The reduced Ru moment, and as a result the weak SVP, do not mask the expulsion of the flux lines at Tc.
KW - Coexistence
KW - Magnetism
KW - Magneto-optical
UR - http://www.scopus.com/inward/record.url?scp=0343832841&partnerID=8YFLogxK
U2 - 10.1016/S0921-4534(00)00658-4
DO - 10.1016/S0921-4534(00)00658-4
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AN - SCOPUS:0343832841
SN - 0921-4534
VL - 341-348
SP - 715
EP - 718
JO - Physica C: Superconductivity and its Applications
JF - Physica C: Superconductivity and its Applications
IS - PART 3
ER -