Phase Transitions in Magnetic and Superconducting Systems with Fluctuating Valence. Chemical Potential Evidence

E. Gosławskaa, M. Matlaka and Kh. Eidb a Institute of Physics, Silesian University, Uniwersytecka 4, 40-007 Katowice, Poland bPhysics Department, Faculty of Education, Ain-Shams University, Roxy, Cairo, Egypt

Received: November 18, 1999

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We investigate the critical behaviour of the chemical potential and average occupation numbers using the extended s -f model with intersite Cooper pairing for systems with fluctuating valence. The model is able to describe phase transitions from normal ferromagnet to normal paramagnet at T=TC, from superconducting paramagnet to normal paramagnet at T=TS, as well as reentrant phase transitions with three critical temperatures TS1, TC and TS2 (TS1 < TC < TS2). Present investigation, as well as recent results obtained for another models suggest one-to-one correspondence between critical temperatures of the system and kinks appearing in the temperature dependence of the chemical potential and average occupation numbers. This, in turn, indicates a possibility to apply the measurement of the chemical potential vs. temperature as an experimental universal tool when looking for phase transitions in solids.

DOI: 10.12693/APhysPolA.97.713 PACS numbers: 75.30.Kz, 75.40.Cx