Evidence for an enhanced magnetoresistance accompanying a continuous phase transition in semiconducting La0.67Mg0.33MnO3

The field- and temperature-dependent ac susceptibility of Mg-substituted LaMnO3 provides unequivocal evidence for the presence of critical fluctuations associated with a continuous paramagnetic-to-ferromagnetic transition at which all three static critical exponents are estimated independently. Furthermore, this system does not undergo a metal-insulator transition near Tc, exhibiting a monotonic increase in resistivity with decreasing temperature in available fields. Nevertheless, this system displays a near colossal magnetoresistance that peaks near Tc, indicating a probable magnetic origin for this effect but of rather different character from that found in other perovskites. copyright 1997 The American Physical Society