Critical exponents of the ferromagnetic-paramagnetic phase transition of La 1 − x Sr x CoO 3 ( 0.20 <~ x <~ 0 . 3 0 )

MIRA, J.; RIVAS, J.; VÁZQUEZ, M.; GARCÍA-BENEYTEZ, J. M.; ARCAS, J.; SÁNCHEZ, R. D.; SEÑARÍS-RODRÍGUEZ, M. A.

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

APS

Lugar: NY; Año: 1999 vol. 59 p. 123 - 126

0163-1829

The critical exponents of the second-order ferromagnetic-paramagnetic phase transition of La1−xSrxCoO3 (0.20<~x<~0.30) compounds are obtained. The results 0.43<~β<~0.46, 1.39<~γ<~1.43, and 4.02<~δ<~4.38 are qualitatively different than those reported in the literature for parent manganites, and are taken as the indication of the absence of long-range interactions below the Curie point. Electronic phase segregation in hole-rich ferromagnetic and hole-poor LaCoO3-like regions is supposed to explain the observations. The hole-poor regions would dilute the magnetic lattice and prevent the occurrence of long-range order. Also, a spin transition of the Co3+ ions at TC or the hole-poor regions (acting equivalently to missed spin clusters in amorphous ferromagnets) could be the reason for the high β value in the framework of a Heisenberg model.