Enhancement Of Room-Temperature Magnetoresistance In Sr2femoo6 By Reducing Its Grain Size And Adjusting Its Tunnel-Barrier Thickness

The intergrain magnetoresistance (IMR) of polycrystalline Sr2FeMoO6 is known to depend on its grain size and the tunnel barrier thickness formed during fabrication. Further enhancement of the IMR of Sr2FeMoO6 is found possible by further decreasing its grain size using high-energy ball milling, as well as by judiciously adjusting the tunnel barrier thickness. The tunnel barrier thickness depends on the amount of insulating nonmagnetic SrMoO4 impurity formed during fabrication, which in turn can be controlled by varying the mixture ratio of the ambient gaseous H-2-Ar stream during annealing. With smaller grain size, the magnetic domain size decreases correspondingly and so can be more easily rotated to produce a lower coercive field. The increase in the SrMoO4 impurity phase increases the number of grain boundary barriers in the Sr2FeMoO6 matrix, leading to a larger low-field magnetoresistance effect (LFMR). A significant enhancement of the LFMR was found when the SrMoO4 impurity was close to the conduction threshold. Compared to the artificial fabrication of multilayer structures, our method is much simpler and offers an enhanced technology to fabricate suitable tunneling barriers in magnetoresistive devices. (C) 2003 American Institute of Physics.