Magnetic properties of Co doped ZSM-5 zeolites

P. G. BERCOFF; H. R. BERTORELLO; C. SAUX; L. B. PIERELLA; P. BOTTA; J. RIVAS

San Sebastián, España

Simposio; III Joint European Magnetic Symposia; 2006

In this work we study the magnetic properties of ZSM-5 zeolites modified with Co cations by wet impregnation and subsequent heat treatments (calcination at 500ºC and reduction in H2). X ray diffraction confirms that the incorporation of the Co ions does not affect neither the cristallinity nor the orthorrombic symmetry of the resultant samples, and in all of them it is noticed the presence of  Co3O4. Only in the reduced samples we detect metallic Co in a cubic phase, and some traces of hexagonal Co only in the sample with more concentration of the dopant.             We measure  the magnetization M as a function of the temperature T (FC and ZFC curves). In the ZFC curves of the samples with more Co concentration we observe a blocking temperature at 7K and a couple of wide peaks around 170K and 250K. We also measure M vs. H/T (where H is the applied field) and we observe a superparamagnetic behavior only in the samples with less Co concentration.             We interpret the results considering the presence of different magnetic clusters in the zeolite.