Identiﬁcation of ﬁrst- and second-order magnetic phase transitions in ferromagnetic perovskites

by **Algerien1970** Tue 16 Jun - 0:50

Identiﬁcation of ﬁrst- and second-order magnetic phase

transitions in ferromagnetic perovskites

J.Miraa,

*, J.Rivas

a

, F.Rivadullab

, M.A. L! opez Quintelab

a

Departmento de F! ısica Aplicada, Universidade de Santiago de Compostela, E-15782 Santiago de Compostela, Spain

b

Departmento de Qu! ımica-F! ısica, Universidade de Santiago de Compostela, E-15782 Santiago de Compostela, Spain

Abstract

A criterion used for the determination of ﬁrst- and second-order magnetic phase transitions from purely magnetic methods is applied to manganese perovskites of formula La2=3ðCa1xSrxÞ1=3MnO3: A crossover from ﬁrst- to second-order character at a tolerance factor t ¼ 0:92 is found, which also brings about several variations in other physical properties.At t ¼ 0:92 a change from orthorhombic to rhombohedral symmetry also takes place.The impossibility of establishing static cooperative Jahn–Teller distortions in the rhombohedral symmetry is suggested as being responsible
for the observed behaviour. r 2002 Elsevier Science B.V. All rights reserved.

Keywords: Manganites; Phase transitions; Jahn–Teller distortion

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