The magnetic and magnetotransport properties of the manganites, R1-xAxMnOz (R = La, Pr, Nd; A = Ca, Sr, Ba), are strongly dependent on the doping level x and the oxygen stoichiometry z. For x ≥ ∼ 0.2, stoichiometric R1-xAxMnO3 was found to have a small temperature independent coercivity of 5-30 Oe and the saturation magnetization (∼ 90 emu/g) of fully aligned Mn ions. Oxygen deficient (or x < 0.2) R1-xAxMnOz has a saturation magnetization smaller than that of fully aligned Mn spins and shows an enhancement and temperature dependence of the coercivity, and spin freezing behavior. The latter is characterized by a peak in zero field cooled (ZFC) magnetization. Our data suggest that oxygen deficient or low doped manganites are magnetically inhomogeneous. We discuss possible origins of the magnetic inhomogeneity and its influence on the colossal magnetoresistance.
Bibliographical noteFunding Information:
The authors thank NSF-DMR 9510474 for partial support of this work. The authors also thank Drs. A.K. Raychaudhuri and T. Venkatesan, and R.L. Greene, R. Ramesh, S. Bhagat, G.C. Xiong, T. Clinton, and Qi Li for useful discussions.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics