TY - JOUR
T1 - Possible origin of the higher magnetic phase transition in RuSr 2Eu 1.5Ce 0.5Cu 2O 10
AU - Felner, I.
AU - Galstyan, E.
AU - Nowik, I.
PY - 2005/2
Y1 - 2005/2
N2 - Two magnetic transitions are observed in the magnetosuperconducting RuEu 2-xCe x-Sr 2Cu 2O 10-δ (Ru-1222), at T M∼ 160 K and T M2 ∼ 80 K. Below T M2 the Ru moments are weak-ferromagnetically ordered and wide ferromagnetic hysteresis loops are observed; they become narrow and disappear at ∼60-70 K. Above T M2, (i) small antiferromagneticlike hysteresis loops reappear with a peak in the coercive fields around 120 K. (ii) A small peak at ∼ 120 K is also observed in the dc and ac susceptibility curves. The two phenomena are absent in the non-SC x=1 samples. For x<1, the decrease of the Ce 4+ content is compensated by nonhomogeneous oxygen depletion, which may induce a reduction of Ru 5+ ions to Ru 4+. The higher ordering temperature, T M, which does not change with x, may result from Ru 4+ rich clusters, in which the Ru 4+-Ru 4+ exchange interactions are stronger than the Ru 5+-Ru 5+ interactions. In the superconducting Ru 1-xMO xSr 2Eu 1.5Ce 0.5Cu 2O 10 (x=0-0.4) system, T M2 shifts to low temperature with x (14 K for x=0.4), whereas T M is not affected by the Mo content, indicating again that T M may not correspond to the main phase. Two scenarios are suggested to explain the magnetic phenomena at T M2M. (i) They are due to a small fraction of nanosize islands inside the crystal grains, in which the Ru 4+ concentration is high and are magnetically ordered below T M. (ii) The presence of nanoparticles of a foreign minor extra Ru 4+ magnetic phase of Sr-Cu-Ru-O 3, which orders at T M, in which Cu is distributed inhomogeneously in both the Ru and Sr sites. This second scenario is supported by Mössbauer spectroscopy of 57Fe doped in Sr-Cu-Ru-O 3 systems.
AB - Two magnetic transitions are observed in the magnetosuperconducting RuEu 2-xCe x-Sr 2Cu 2O 10-δ (Ru-1222), at T M∼ 160 K and T M2 ∼ 80 K. Below T M2 the Ru moments are weak-ferromagnetically ordered and wide ferromagnetic hysteresis loops are observed; they become narrow and disappear at ∼60-70 K. Above T M2, (i) small antiferromagneticlike hysteresis loops reappear with a peak in the coercive fields around 120 K. (ii) A small peak at ∼ 120 K is also observed in the dc and ac susceptibility curves. The two phenomena are absent in the non-SC x=1 samples. For x<1, the decrease of the Ce 4+ content is compensated by nonhomogeneous oxygen depletion, which may induce a reduction of Ru 5+ ions to Ru 4+. The higher ordering temperature, T M, which does not change with x, may result from Ru 4+ rich clusters, in which the Ru 4+-Ru 4+ exchange interactions are stronger than the Ru 5+-Ru 5+ interactions. In the superconducting Ru 1-xMO xSr 2Eu 1.5Ce 0.5Cu 2O 10 (x=0-0.4) system, T M2 shifts to low temperature with x (14 K for x=0.4), whereas T M is not affected by the Mo content, indicating again that T M may not correspond to the main phase. Two scenarios are suggested to explain the magnetic phenomena at T M2M. (i) They are due to a small fraction of nanosize islands inside the crystal grains, in which the Ru 4+ concentration is high and are magnetically ordered below T M. (ii) The presence of nanoparticles of a foreign minor extra Ru 4+ magnetic phase of Sr-Cu-Ru-O 3, which orders at T M, in which Cu is distributed inhomogeneously in both the Ru and Sr sites. This second scenario is supported by Mössbauer spectroscopy of 57Fe doped in Sr-Cu-Ru-O 3 systems.
UR - http://www.scopus.com/inward/record.url?scp=84856128292&partnerID=8YFLogxK
U2 - 10.1103/PhysRevB.71.064510
DO - 10.1103/PhysRevB.71.064510
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AN - SCOPUS:84856128292
SN - 1098-0121
VL - 71
JO - Physical Review B - Condensed Matter and Materials Physics
JF - Physical Review B - Condensed Matter and Materials Physics
IS - 6
M1 - 064510
ER -