Metal-insulator transition in helical SrFeO3-δ antiferromagnet

The magnetic and electrical transport properties of metallic spiral antiferromagnet SrFeO2.95 have been examined in the temperature range from 4.5-300 K. A large negative magnetoresistance below 50 K is observed. We find hysteresis in resistivity in 0 and 9T due to the coexistence of antiferromagnetic and paramagnetic domains in the temperature region 50-80 K. The metal insulator transition temperatures can be tuned by applying magnetic fields. The low-temperature conductivity, sigma(T --> 0) obeys a critical law of the form sigma(T --> 0) proportional to [E-F(0) - E-C](nu) equivalent to (H - H-C)(nu) with nu = 1, where H-C is a critical field and E-C the mobility edge. Such behavior is consistent with scaling theories of both localization and interaction effects. The observation of the present study indicates that the electronic states become more extended with increasing field. (C) 2004 Elsevier B.V. All rights reserved.