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

Abstract

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 codoping 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 Ω 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.

Atomic-scale insights into quantum-order parameters in bismuth-doped iron garnet

“…Although pure yttrium iron garnet (YIG) has several advantages in terms of magneto-optical response, it has not been widely applied in integrated devices due to its low Verdet constant, resulting in a limited Faraday rotation (23,24). Due, however, to its chemical flexibility, selective substitution has been established as an effective method to tune various physical properties of iron garnets (7,12,25,26), and it is noteworthy that Bi-substituted lutetium iron garnet films prepared via liquid phase epitaxy (LPE) demonstrate an appreciable enhancement in magneto-optical performance (8). Several models based on diamagnetic transitions have been proposed to explain the effect of Bi substitution on magnetooptical response (4,12,17,19,21,(27)(28)(29)(30), in each case with a strong dependence on the crystal energy levels of the Fe 3+ ions in differently coordinated lattice sites.…”

Direct mapping of electronic orbitals in graphene using electron energy-loss spectroscopy

“…Electron energy-loss spectroscopy (EELS) in an electron microscope is a spectroscopy technique probing site-and momentum-projected empty states in the conduction band [10]. Following the development of aberration correctors and high stability electron-optics, atomic resolution EELS in the scanning transmission electron microscope (STEM) has become routinely available, leading to elemental (chemical) mapping [11][12][13], and providing real-space atomic scale localization of electronic states [14][15][16][17][18][19][20] using the energy-loss near-edge structure (ELNES) of the spectroscopic signal.…”

Electronic Structure and Chemistry of Nanomaterials Embedded in a Matrix Using Atomically Resolved Near-edge Structures: The Example of Ferromagnetic Ni Nanowires Grown in SrTiO3

“…Such information about the electronic structure are reflected into the spectral fine structures above the Fermi level, the energy-loss near edge structures (ELNES), and provide a wealth of information to understand the structure and chemistry interplay in e.g. thin films [1], nanostructured bulk materials [2], and composite systems with embedded nanomaterials [3,4]. With a monochromator, the large majority of spectral features in core level excitation are resolved at and above the edge onset.…”