Interplay between epitaxial strain and low dimensionality effects in a ferrimagnetic oxide

Abstract

Thin film properties are strongly influenced by strain and low dimensionality effects, especially when the film thickness is about a few unit cells, which corresponds to the thicknesses targeted in most of contemporary studies. In oxides, these effects are responsible for the dramatic modification of the physical properties that sometimes can change the nature of a material. Nevertheless, it is not always possible to distinguish the contribution of the strain to the changes in physical properties from the contribution due to low dimensional effects. In the present study, bismuth iron garnet Bi3Fe5O12 (BIG) is chosen to separate both effects. This material possesses, among other outstanding physical properties, the giant Faraday rotation that allows investigating films with the thickness below a few unit cells. Three series of BIG films of various thicknesses were grown on three isostructural substrates with different lattice parameters: Y3Al5O12(001), Gd3Ga5O12(001), and (GdCa)3(GaMgZr)5O12(001). The structural, magnetic, and magneto-optic properties were studied as a function of film thickness and strain. Furthermore, critical behavior of the BIG films was investigated in the vicinity of the Curie temperature. The obtained results allowed distinguishing between the low dimensional effects and the strain due to the epitaxial growth. While the size reduction is mostly responsible for the decrease of the magnetic characteristics of the films, the strain influences rather the critical thickness below which the material starts to behave as a low dimensional system.

Ultrafast control of lattice strain via magnetic circular dichroism

“…The absence of any other diffraction peaks indicates the single-crystalline and single-phase nature the BIG film. This is in agreement with transmission electron microscopy measurements in BIG samples obtained in identical growth conditions [50]. The width of the BIG Bragg reflection q z = 0.007 Å −1 and the Laue oscillations indicate that the coherence length coincides with the film thickness.…”

Bismuth iron garnet: Ab initio study of electronic properties

“…From Fig. 1 panel (b) it emerges that: (i) the PBE and PBEsol theoretical optimized BIG lattice parameters differ from the experimental lattice constant of the garnet substrates by an amount of 1% to 5%, as experimentally observed 33 (ii) the theoretical lattice constants optimized with PBEsol+U for U among 2 and 4.5 eV fall into the experimental range of variation indicated by the yellow bar in Fig. 1.…”

“…Y 3 Al 5 O 12 (YAG), Gd 3 Ga 5 O 12 (GGG) or substituted GGG (SGGG) having smaller lattice constants than of BIG (12Å (YAG), 12.37Å (GGG) and 12.48Å (SGGG) respectively 32,33 ) that result in compressive strain to the BIG film. Therefore the measurement of the absolute value of the lattice constant remains particularly challenging 33 . In this context, the experimental lattice constant of BIG thin films varies according to literature between 12.60 and 12.633Å [34][35][36] , while polycrystalline 37 and monocrystalline 38 BIG films have reported to present slightly larger values of 12.64 or 12.65Å.…”

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

“…Bi 3 Fe 5 O 12 (BIG), Bi 2.5 Y 0.5 Fe 5 O 12 (B(Ca 0.0 Y 0.5 )IG), and Bi 2.5 Ca 0.3 Y 0.2 Fe 5 O 12 (B(Ca 0.3 Y 0.2 )IG) thin films of about 150 nm thick were grown by PLD onto GGG substrates. The BIG targets substituted with Ca and Y were prepared from high purity powders (99.99% for Ca precursor and 99.999% for all other precursors) using a standard ceramic processing method . An excimer KrF laser with a wavelength of 248 nm and pulse duration of 20 ns was used for film deposition.…”