First principles calculation on the magnetic, optical properties and oxygen vacancy effect of CexY3−xFe5O12

Abstract

We report a first principles study on the magnetic and optical properties of Ce substituted yttrium iron garnet (CexY3−xFe5O12) (Ce:YIG) (x = 0.125, 0.25, 0.5, and 1.0). Using density functional theory with Hubbard-U corrections, we demonstrate that Ce3+-Fe3+(tetrahedral) charge transfer is the dominating mechanism of enhanced near infrared absorption in Ce:YIG. In particular, oxygen vacancies are found to be able to stabilize Ce3+ from converting to Ce4+, at the same time reduce two neighboring Fe3+ to Fe2+ which occupy both the octahedral and tetrahedral sites. The formation enthalpy of Ce4+-Fe2+ state is strongly dependent on the distance from the Ce ion to the oxygen vacancy, which is closely related to the local lattice distortion around the Ce ion. This result provides theoretical insight for developing high figure of merit magneto-optical materials for nonreciprocal photonic applications.

Direct observation of multivalent states and 4f→3d charge transfer in Ce-doped yttrium iron garnet thin films

“…Indeed, Ce 4+ states have been reported for other Ce oxide structures, and their origin has been attributed to the hybridization between Ce 4f and neighboring O 2p or transition-metal 3d bands [34,35]. From first-principles calculations reported for the Ce-YIG system, it is known that the charge transfer takes place from Ce(4f ) to Fe(3d) states at d-(tetrahedral) sites [14]. In the following, we show that this prediction is confirmed by the analysis of our XMCD spectra and further supported by multiplet XMCD calculations.…”

“…Yet, despite the remarkable potential applications in optics, the fundamental physical mechanisms behind the enhanced magneto-optical response of Ce-YIG films are still being debated. Mostly, two types of electronic transitions are proposed, viz., either (i) intra-atomic orbital dipole transitions between the 4f and 5d states of Ce or (ii) interatomic dipole transitions between the 4f states of Ce and 3d states of Fe [7,[14][15][16]. It is unclear, however, whether both transitions are involved or if one of them prevails over the other.…”

Untangling the contributions of cerium and iron to the magnetism of Ce-doped yttrium iron garnet

“…In view of this, untangling the individual contributions of Ce and Fe may provide further clues to a better understanding of the nature of the magneto-optical enhancement in doped YIG and the character of the assigned electronic transitions 24,25 . In this sense, exploiting the wavelength selectivity of YIG's gyrotropic response may also help solving some controversial issues that are still today a matter of debate, regarding the fundamental mechanisms that rule the magneto-optical enhancement of these compounds 26 .…”

“…For instance, peering into the different sublattice gyrotropic responses may shed light on the specific dynamics of the magnetic moments of the different cations, something that is unattainable for other experimental methods. On the other hand, time-resolved experiments may also provide indirect ways to peer into the nature of the involved transitions, an issue that is still nowadays a matter of debate 26 . Two basic transitions are proposed: either between 4f and 5d states of Ce 3+ or between 4f and 3d states of Ce 3+ and Fe at the tetrahedral site 26,42 .…”

A first-principles study of strain tuned optical properties in monolayer tellurium

“…13 It is well acknowledged that property modulation is a hot issue, especially for 2D materials. [14][15][16][17][18][19][20][21][22][23] Among those, it can be seen that strain is one of the most used methods and an effective and promising way to modify the physical properties of 2D materials. For example, local strain can modulate the optical gap and enhance light emission in ReSe 2, as well as increase visible light absorption of ScNbCO 2 .…”