title: Tricritical point and the doping dependence of the order of the ferromagnetic phase transition of La1-xCaxMnO3.
abstract: We report on the doping dependence of the order of the ferromagnetic metal to paramagnetic insulator phase transition in La1-xCaxMnO3. At x=0.33, magnetization and specific heat data show a first order transition, with an entropy change (2.3 J/mol K) accounted for by both volume expansion and the discontinuity of M approximately 1.7mu(B) via the Clausius-Clapeyron equation. At x=0.4, the data show a continuous transition with tricritical point exponents alpha=0.48+/-0.06, beta=0.25+/-0.03, gamma=1.03+/-0.05, and delta=5.0+/-0.8. This tricritical point separates first- (x<0.4) from second-order (x>0.4) transitions.
authors.affiliation: Department of Physics, University of California, San Diego, La Jolla 92093, USA.
authors.forename: D
authors.initials: D
authors.lastname: Kim
authors.forename: B
authors.initials: B
authors.lastname: Revaz
authors.forename: B L
authors.initials: BL
authors.lastname: Zink
authors.forename: F
authors.initials: F
authors.lastname: Hellman
authors.forename: J J
authors.initials: JJ
authors.lastname: Rhyne
authors.forename: J F
authors.initials: JF
authors.lastname: Mitchell