Spin state of Co3+ and magnetic transitions in RBaCo2O5.50 ?R=Pr,Gd?: Dependence on rare-earth size
C. FRONTERA; J.L. GARCÍA MUÑOZ; A.E. CARRILLO; M.A.G. ARANDA; I. MARGIOLAKI; A. CANEIRO
PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS
American Physical Society
Año: 2006 vol. 74 p. 544061 - 544061
We have studied the magnetic and structural properties of PrBaCo2O5.50 and GdBaCo2O5.50 using neutronand synchrotron techniques between 10 and 425 K. A unique structural transition has been detected in thistemperature range. The changes observed in Co?O bond lengths across the metal-insulator transition confirmthe spin state change of octahedral Co ions with R=Pr, the member of the RBaCo2O5.50 family with the largestR-ion and R/Ba order. Magnetic structures have been thoroughly investigated. Different magnetic modelspreviously reported for smaller lanthanides were checked against our data. We have found an evolution of themagnetic order, across the successive magnetic transitions, which can be interpreted on the basis of a hierarchicalset of exchange interactions.