Non-collinear magnetic ordering in the perovskite compound YFe 1/4 Cr 3/4 O 3 A. Dahmani a,b, * , M. Taibi b , J. Aride b , A. Belayachi a , M. Nogues c a Laboratoire de Physique des Mate´riaux, Faculte´ des Sciences, Universite´ Mohammed V, B.P. 1014 Rabat, Morocco b Laboratoire de Physico-chimie des Mate´riaux, Associe´a` l’AUF (LAF 502) ENS, B.P. 5118 Takaddoum, Rabat, Morocco c Laboratoire de Magne´tisme et d’Optique de l’Universite´ de Versailles (URA 1531), Batiment Fermat, 45 Avenue des Etats Unis, 78035 Versailles Cedex, France Received 4 May 2001; received in revised form 29 August 2001; accepted 2 September 2001 Abstract The polycrystalline compound YFe 0.25 Cr 0.75 O 3 , prepared by solid reaction in air exhibits the perovskite structure with orthorhombic deformation. Its space group is Pbnm. High temperature d.c. magnetic susceptibility and magnetization studies have been carried out. The measurements revealed non-collinear magnetic behaviour. The occurrence of hysteresis loops and compensation effects suggests ferrimagnetic arrangements. The results are explained qualitatively assuming the presence of two uncompensated weak ferromagnets. The zero-field-cooled (ZFC) and field-cooled (FC) magnetization curves merge at a temperature well above the Ne´el’s one. This suggests the occurrence of short-range magnetic order, which is induced by frustration effects. The frustration in this case results from the structural disorder due to the random distribution of the magnetic ions in the octahedral sites of the lattice. D 2002 Elsevier Science B.V. All rights reserved. Keywords: Perovskite; Weak ferrimagnetism; Frustration; Compensation; Hysteresis; Phase transition 1. Introduction Perovskite oxides of the general formula ABO 3 with rare earth, or yttrium, on the A site and transi- tion metals on the octahedral B site have been a subject of numerous studies [1–4]. They are well known for their catalytic activities and wide range of electrical and magnetic properties. These compounds have recently regained much interest as cathode in solid oxide fuel cells (SOFC) [5] and as possible future magneto-optic storage materials [6]. On the other hand, since the discovery of giant magneto- resistance in many of these perovskite oxides, they became promising candidates for a next generation of magnetic sensors and magnetic refrigerators [7]. The interesting properties of these systems are directly related to the nature of ions occupying the A and B sites. The large possibilities to substitute them permit to modulate several of these properties. The substitution of La by alkaline-earth ions in LaMnO 3 transforms the compound from an antiferromagnetic insulator to a ferromagnetic metal [8]. In the system LaNi 1 x Fe x O 3 , a metal–insulator transition takes place for a Fe 3+ concentration  f 0.3 [9]. Several 0167-577X/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved. PII:S0167-577X(01)00580-8 * Corresponding author. Laboratoire de Physique des Mate´ri- aux, Faculte´ des Sciences, Universite´ Mohammed V, B.P. 1014 Rabat, Morocco. E-mail address: dahm19@yahoo.fr (A. Dahmani). www.elsevier.com/locate/matlet June 2002 Materials Letters 54 (2002) 291 – 297