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

Abstract

Due to their large magneto-optic responses, rare-earth-doped yttrium iron garnets, Y 3 Fe 5 O 12 (YIG), are highly regarded for their potential in photonics and magnonics. Here, we consider the case of Ce-doped YIG (Ce-YIG) thin films, in which substitutional Ce 3+ ions are magnetic because of their 4f 1 ground state. In order to elucidate the impact of Ce substitution on the magnetization of YIG, we have carried out soft x-ray spectroscopy measurements on Ce-YIG films. In particular, we have used the element specificity of x-ray magnetic circular dichroism to extract the individual magnetization curves linked to Ce and Fe ions. Our results show that Ce doping triggers a selective charge transfer from Ce to the Fe tetrahedral sites in the YIG structure. This, in turn, causes a disruption of the electronic and magnetic properties of the parent compound, reducing the exchange coupling between the Ce and Fe magnetic moments and causing atypical magnetic behavior. Our work is relevant for understanding magnetism in rare-earth-doped YIG and, eventually, may enable a quantitative evaluation of the magneto-optical properties of rare-earth incorporation into YIG.

Interfacial Dzyaloshinskii-Moriya interaction arising from rare-earth orbital magnetism in insulating magnetic oxides

“…The procedure is described in detail in refs. 41,42 . We first multiplied each spectrum with a constant factor such that the average intensity in the pre-and post-edge regions of all spectra aligned.…”

Direct observation of coherent magnons with suboptical wavelengths in a single-crystalline ferrimagnetic insulator

“…Circularly polarized x rays were focused to a spot of 18 nm diameter using a diffractive Fresnel zone plate. The x-ray energy was always set to one of the three local maxima of the dichroic signal at the iron L 3 -absorption edge (E ∼ 710 eV) [35]. Time-resolved measurements were achieved by using a stroboscopic pump-and-probe technique, for which the temporal resolution is given by the time spread of the probing x-ray flashes, i.e., ∼70 ps during the synchrotron's regular multibunch mode operation and ∼10 ps in the low alpha mode [24] (contributions from the electronic pump signal of the experiment are usually negligible in comparison).…”

“…Figure 2 displays an example of a recorded spin wave in a 185 nm YIG-film sample. For this thicker sample the x-ray energy was set to the first of the three XMCD maxima in order to maximize transmission [35]. Part (a) shows the direct x-ray image of the ion beam etched window, with one stripline antenna being clearly visible as a darker bar in the center.…”

Role of Ce concentration on the structural and magnetic properties of functional magnetic oxide particles

“…Specifically, the study of bismuth and cerium substituted YIG has attracted a lot of interest due to their high Faraday rotation and strong magneto-optical activity in near infrared telecommunication wavelengths [52,53,56,65]. Cerium (Ce) element has amazing quality as it can be effortlessly exchangeable between 4+ valence state and 3+ valence state [66]. Also, cerium substituted yttrium iron oxide attracted much attention due to their remarkable multiferroic (MF) properties such as magnetodielectric (MD) and strong magneto-optical (MO) effects [67][68][69].…”