Inter-grain tunneling in the half-metallic double-perovskites Sr2BB'O6 (BB'-- FeMo, FeRe, CrMo, CrW, CrRe
Abstract
The zero-field conductivities (σ) of the polycrystaline title materials, are governed by inter-grain transport. In the majority of cases their σ(T) can be described by the "fluctuation induced tunneling" model. Analysis of the results in terms of this model reveals two remarkable features: 1. For all Sr2FeMoO6 samples of various microstructures, the tunneling constant (barrier width × inverse decay-length of the wave-function) is 2, indicating the existence of an intrinsic insulating boundary layer with a well defined electronic (and magnetic) structure. 2. The tunneling constant for all cold-pressed samples decreases linearly with increasing magnetic-moment/formula-unit.
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