Magnetic properties of La1-xCexCrO3

We present a study of the magnetic properties of La1-xCexCrO3 performed by DC magnetization and electron spin resonance (ESR) techniques. The susceptibility χ(T) for x=0 shows an anomaly at TS=535 (5)K, which we associate to a structural rombohedral-orthorhombic transition. Above and below TS, χ(T) follows a Curie-Weiss (CW) law and we determine C=1.99(1)emu/molK, and Θ =-800 (7)K. The existence of competing interactions was manifested in the relatively low value of TN=288 (3)K [Θ/TN∼3] and by the development of a weak FM component below TN. For x<>0, the observed changes in χ(T) may be explained by considering that Ce is trivalent. These observations contrast with the series Ca1-xCexMnO3 (Cr3+ and Mn4+ are isoelectronic) where Ce was present as Ce4+. Dramatic effects on the ESR spectrum of La1-xCexMnO3 were observed as a function of x and the x=0.20 spectrum is not more visible. Relaxation mechanisms compatible with S>12 resonant ions should be proposed in order to describe the ESR behavior