Percolation processes and spin-reorientation of PrNi5-xCox


In the present work we report on the structural and magnetic behaviors of the PrNi5-xCox intermetallic compounds. Due to the competition between the anisotropy energies of both Co and Pr sublattices, this series has a spin-reorientation phenomenon at low temperature (140 K). The Curie temperature, as a function of Co content, has a sudden increase above a critical concentration x(c)similar to 1.9 and this feature is assigned as a percolation of geometrically spaced Co clusters. This assumption is explained based on the critical exponent of percolation theory. The series presents therefore a rich magnetic phase diagram, which could be established over a full doping range, i.e., from x=0 to x=5. We have also studied these compounds on the magnetocaloric point of view and found a quite large full width at half maximum (delta T-FWHM) of the magnetic entropy change curves for some of the compositions, due to the merging of the Delta S peaks associated with the spin-reorientation process and the Curie temperature T-C. In addition, the series has an appreciable relative cooling power, which is therefore suitable to be used in a magnetic refrigerator operating in a large range of temperature.






Rocco, DL; Amaral, JS; Leitao, JV; Amaral, VS; Reis, MS; Fernandes, RP; Pereira, AM; Araujo, JP; Martins, NV; Tavares, PB; Coelho, AA

nossos autores


The authors thank FCT for the VSM equipment (Grant No. REEQ/1126/2001) and the project POCI/CTM/61284/2004. D. L. R. thanks CICECO and FCT (Grant No. SFRH/BPD/41927/2007) for the grant.

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