In this paper we report a detailed $\mu^{+}$SR and {}$^{19}$F-NMR study of the La$_{0.7}$Y$_{0.3}$FeAsO$_{1-x}$F$_{x}$ class of materials. Here, the diamagnetic La$_{1-y}$Y$_{y}$ substitution increases chemical pressure and, accordingly, sizeably enhances the optimal superconducting transition temperature. We investigate the magnetic-superconducting phase transition by keeping the Y content constant ($y = 0.3$) and by varying the F content in the range $0.025 \leq x \leq 0.15$. Our results show how magnetism and superconductivity coexist for $x = 0.065$. Such coexistence is due to segregation of the two phases in macroscopic regions, resembling what was observed in LaFeAsO$_{1-x}$F$_{x}$ materials under applied hydrostatic pressure. This scenario is qualitatively different from the nanoscopic coexistence of the two order parameters observed when La is fully substituted by magnetic rare-earth ions like Sm or Ce.
Phase separation at the magnetic-superconducting transition in La0.7Y0.3FeAsO1-xFx / Giacomo Prando; Samuele Sanna; Gianrico Lamura; Toni Shiroka; Matteo Tropeano; Andrea Palenzona; Hans-Joachim Grafe; Bernd Buchner; Pietro Carretta; Roberto De Renzi. - In: PHYSICA STATUS SOLIDI. A, APPLICATIONS AND MATERIALS SCIENCE. - ISSN 1862-6319. - STAMPA. - 250:3(2013), pp. 599-602. [10.1002/pssb.201200767]
Phase separation at the magnetic-superconducting transition in La0.7Y0.3FeAsO1-xFx
SANNA, SAMUELE;
2013
Abstract
In this paper we report a detailed $\mu^{+}$SR and {}$^{19}$F-NMR study of the La$_{0.7}$Y$_{0.3}$FeAsO$_{1-x}$F$_{x}$ class of materials. Here, the diamagnetic La$_{1-y}$Y$_{y}$ substitution increases chemical pressure and, accordingly, sizeably enhances the optimal superconducting transition temperature. We investigate the magnetic-superconducting phase transition by keeping the Y content constant ($y = 0.3$) and by varying the F content in the range $0.025 \leq x \leq 0.15$. Our results show how magnetism and superconductivity coexist for $x = 0.065$. Such coexistence is due to segregation of the two phases in macroscopic regions, resembling what was observed in LaFeAsO$_{1-x}$F$_{x}$ materials under applied hydrostatic pressure. This scenario is qualitatively different from the nanoscopic coexistence of the two order parameters observed when La is fully substituted by magnetic rare-earth ions like Sm or Ce.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.