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Atmosphere-Induced Reversible Resistivity Changes in Ca/Y-Doped Bismuth Iron Garnet Thin Films

Resistive changes in Y-substituted bismuth iron garnet (BIG)

Bismuth iron garnet Bi3Fe5O12 (BIG) is a multifunctional insulating oxide exhibiting remarkably the largest known Faraday rotation and linear magnetoelectric coupling. Enhancing the electrical conductivity in BIG while preserving its magnetic properties would further widen its range of potential applications in oxitronic devices. Here, a site-selective co-doping strategy in which Ca2+ and Y3+ substitute for Bi3+ is applied. The resulting p- and n-type doped BIG films combine state-of-the-art magneto-optical properties and semiconducting behaviors above room temperature with rather low resistivity: 40 Ohm cm at 450 K is achieved in an n-type Y-doped BIG; this is ten orders of magnitude lower than that of Y3Fe5O12. High-resolution electron spectromicroscopy unveils the complete dopant solubility and the charge compensation mechanisms at the local scale in p- and n-type systems. Oxygen vacancies as intrinsic donors play a key role in the conduction mechanisms of these doped BIG films. On the other hand, a self-compensation of Ca2+ with oxygen vacancies tends to limit the conduction in p-type Ca/Y-doped BIG. These results highlight the possibility of integrating n-type and p-type doped BIG films in spintronic structures as well as their potential use in gas sensing applications.