Abstract
A detailed study of the magnetization M(H,T) of manganites near TC is presented. Analysis, in the framework of Landau theory of phase transitions (G=G0+1/2AM2+1/4BM4+1/6CM6−MH) reveals that for La0.67Ca0.33MnO3 (TC=267 K), La0.8MnO3 (TC=250 K), and La0.60Y0.07Ca0.33MnO3 (TC=150 K) the phase transition is first-order and the B coefficient is temperature dependent, negative near TC. In field (H<HC*) and temperature (TC<T<TC*) ranges, below the critical point of the first-order phase transition, clear features are found, with hysteresis. For La0.60Y0.07Ca0.33MnO3, HC*∼20 kOe, ΔT=TC*−TC∼20 K. For La0.67Ca0.33MnO3, on the other hand, HC* is only 250 Oe and ΔT<1 K. These effects are related with electronic and elastic energy contributions coupled to the magnetic order parameter. The analysis of the vanishing of B above TC suggests that a tricritical point should occur at T∼310 K, in agreement with the temperature at which the magnetic and structural transitions in La0.7(Ca1−ySry)0.3MnO3 coincide.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
