M. Roy — Page 2 | Searcharxiv

arXiv2000

Field Dependent Specific-Heat of Rare Earth Manganites

The low temperature specific heat C(H) of several rare-earth manganites (La_(0.7)Sr_(0.3)MnO_(3), Nd_(0.5)Sr_(0.5)MnO_(3), Pr_(0.5)Sr_(0.5)MnO_(3), La_(0.67)Ca_(0.33)MnO$_(3), La_(0.5)Ca_(0.5)MnO_(3), La_(0.45)Ca_(0.55)MnO_(3) and La_(0.33)Ca_(0.67)MnO_(3)) was measured as a function of magnetic field. We observed behaviour consistent with thermodynamic expectations, i.e., C(H) decreases with field for ferromagnetic metallic compounds by an amount which is in quantitative agreement with spin wave theory. We also find that C(H) increases with field in most compounds with a charge-ordered antiferromagnetic ground state. In compounds which show evidence of a coexistence of ferromagnetic metallic and antiferromagnetic charge-ordered states, C(H) displays some unusual non-equilibrium effects presumably associated with the phase-separation of the two states. We also observe a large anomalous low temperature specific heat at the doping induced metal-insulator transition (at x = 0.50) in La_(1-x)Ca_(x)MnO_(3).

cond-mat↗

arXiv2000

Time Dependent Effects and Transport Evidence for Phase Separation in La_{0.5}Ca_{0.5}MnO_{3}

The ground state of La_{1-x}Ca_{x}MnO_{3} changes from a ferromagnetic metallic to an antiferromagnetic charge-ordered state as a function of Ca concentration at x ~ 0.50. We present evidence from transport measurements on a sample with x = 0.50 that the two phases can coexist, in agreement with other observations of phase separation in these materials. We also observe that, by applying and then removing a magnetic field to the mainly charge-ordered state at some temperatures, we can "magnetically anneal" the charge order, resulting in a higher zero-field resistivity. We also observe logarithmic time dependence in both resistivity and magnetization after a field sweep at low temperatures.

cond-mat↗