A study of freezing temperature and magnetic relaxation for epitaxial La0.67Sr0.33MnO3-δ films

The variations of magnetic susceptibility and magnetic relaxation obtained by a superconducting quantum interference device magnetometer are investigated systematically for epitaxial La0.67Sr0.33MnO3-δ films grown on (001) LaAlO3 single-crystal substrate using a direct-current magnetron sputtering technique. Spin-glass-like behaviour can be observed, which is caused by the competition between ferromagnetism and antiferromagnetism, a direct consequence of the random distribution of Mn3+ and Mn4+ ions. Using the concept of spin glass and the double-potential-well model, we have calculated the relation between the applied field and the freezing temperature and the relaxation of M versus time. All the calculated results are in good agreement with the experimental values.