Discontinuous transition effects in manganites: magnetization study in the paramagnetic phase

The magnetization M( H, T) of La-based manganites in the paramagnetic phase is studied. La 0.67Ca 0.33MnO 3, La 0.8MnO 3 and La 0.60Y 0.07Ca 0.33MnO 3 ferromagnetic metals show first-order phase transition features near T C with maxima in d M/d H and kinks in H/ M vs. T. Such effects are absent in ferromagnetic insulator La 0.67Cd 0.25MnO 3. Results are analyzed with a Landau energy expansion up to sixth power in M and the anomalies related with the electronic condensation and magneto-elastic energies coupling to the magnetic degree of freedom.