I. S. Edelman

Magnetic and optical properties and electron paramagnetic resonance of gadolinium-containing oxide glasses

Magnetic susceptibility, electron paramagnetic resonance (EPR) and optical absorption have been studied in a glass system 20La2O3–22Al2O3–23B2O3– 35(SiO2+GeO2) with a part of La2O3 substituted by Gd2O3 in different concentrations. Positive Weiss constants have been found in more heavily doped glasses and ascribed to clustering of Gd3+ ions. Computer simulations of the EPR spectra show that the short-range ordering in the environment of the Gd3+ ions is well preserved. The relative distribution widths of the ligand coordinates are less than 2%. In the more heavily doped glasses the EPR spectra are superpositions of signals arising from isolated ions and ferromagnetic clusters. The increase of Gd3+ concentration is shown to change substantially the strong optical absorption edge while only small changes of f–f absorption band characteristics are observed. This difference is associated with the different effect of the Gd ion clustering on the mechanisms of the strong absorption in the ultraviolet region and the f–f absorption.

Formation and evolution of magnetic nanoparticles in borate glass simultaneously doped with Fe and Mn oxides

Evolution of the phase state of paramagnetic additions at various stages of synthesis and subsequent thermal treatment of glasses of the system Al2O3–K2O–B2O3 simultaneously doped with Fe2O3 and MnO is studied by means of a combination of experimental techniques: Faraday rotation (FR), electron magnetic resonance (EMR), transmission electron microscopy (TEM), Mossbauer spectroscopy, and magnetic measurements. Both FR and EMR show that magnetically ordered clusters occur already at the first stage of the glass preparation. In particular, for the ratio of the Fe and Mn oxides in the charge close to 3:2, fine magnetic nanoparticles are formed with characteristics similar to those of manganese ferrite. By computer simulating the EMR spectra at variable temperatures, a superparamagnetic nature of these nanoparticles is confirmed and their mean diameter is estimated as approximately 3.2 nm. In the thermally treated glasses larger magnetic nanoparticles are formed, giving rise to FR spectra, characteristic of ma...

Magnetic properties of ferrite microparticles in borate glasses

Abstract Magneto-optic Faraday effect in potassium-alumina-borate glasses with Fe 2 O 3 and CoO additions made during synthesis was studied in dependence on the light wavelength, external magnetic field an temperature. It was shown that unusual magnetic properties of these glasses were due to the formation of ferrimagnetic particles which behaved at definite conditions as an ansamble of noninterecting superparamagnetic particles. Dimensions, structure, composition and blocking temperature of the particles have been determined.

Magnetic nanoparticles formed in glasses co-doped with iron and larger radius elements

A new type of nanoparticle-containing glasses based on borate glasses co-doped with low contents of iron and larger radius elements, Dy, Tb, Gd, Ho, Er, Y, and Bi, is studied. Heat treatment of these glasses results in formation of magnetic nanoparticles, radically changing their physical properties. Transmission electron microscopy and synchrotron radiation-based techniques: x-ray diffraction, extended x-ray absorption fine structure, x-ray absorption near-edge structure, and small-angle x-ray scattering, show a broad distribution of nanoparticle sizes with characteristics depending on the treatment regime; a crystalline structure of these nanoparticles is detected in heat treated samples. Magnetic circular dichroism (MCD) studies of samples subjected to heat treatment as well as of maghemite, magnetite, and iron garnet allow to unambiguously assign the nanoparticle structure to maghemite, independently of co-dopant nature and of heat treatment regime used. Different features observed in the MCD spectra ...

Interface effect on the magnetic properties of Ni-Ge bilayer films

Magnetic and magneto-optical properties of the Ni-Ge bilayer films are studied. The unusual temperature behavior of the magnetization curves is revealed: the hysteresis loops at room temperature have a near-rectangular shape; when the films are cooled down to 4.2 K, the coercive force increases by more than an order of magnitude and the asymmetry and displacement of the loop along the field axis are observed. These effects are stronger in thinner Ni layers. The observed features are attributed to the effect of the interlayer between the Ni and Ge layers, which has a complex magnetic structure.

RE containing glasses as effective magneto-optical materials for 200-400 nm range

Magneto-optical Faraday rotation (FR), optical absorption and magnetization of oxide glasses with high concentration of rare earth (RE) ions (up to 25 mol.% of R2O3, R: Pr3+, Dy3+ Eu2-) are investigated. These glasses had a good transparence and high value of Verdet constant simultaneously. They can be considered as materials of high magneto-optical quality in the wavelength range 200-400 nm.

Magneto-optical properties of Dy3+ in oxide glasses: The origin of the magneto-optical activity of f-f transitions and its anomalous temperature dependence

The temperature dependence of the absorption spectra and magnetic circular dichroism due to f-f transitions from the 6H15/2 to 6F5/2 and 6(F7/2 + H5/2) states in the Dy3+ ion in (Dy2O3-P2O5-SiO2-GeO2) and (Dy2O3-La2O3-Al2O3-B2O3-SiO2-GeO2) glasses and the temperature dependence of the Faraday effect were studied. The temperature dependence of the Faraday effect caused by f-d transitions was found to differ from that of the magnetic circular dichroism due to f-f transitions. It was shown that f-f transitions occur preferentially in Dy3+ ions associated into clusters. The origin of the paramagnetic magneto-optical activity of f-f transitions was analyzed. It was shown that the contributions to this activity can differ in value and sign and that the ratio between these contributions depends on the transition type. In some cases, this difference results in an anomalous temperature dependence of the magneto-optical activity.

Magnetic and magneto-optical properties of ion-synthesized cobalt nanoparticles in silicon oxide

The magnetic and magneto-optical properties of ion-synthesized cobalt nanoparticles in the amorphous silicon oxide matrix are investigated as a function of the implantation dose. The analysis of the field dependences of the magnetization and the magneto-optical Faraday and Kerr effects demonstrates that, as the ion implantation dose increases, the superparamagnetic behavior of an ensemble of cobalt nanoparticles at room temperature gives way to a ferromagnetic response with the anisotropy characteristic of a thin magnetic film. The magnetization curves for the superparamagnetic and ferromagnetic ensembles of cobalt nanoparticles are simulated to determine their average sizes and the filling density in the irradiated layer of the silicon dioxide matrix. It is revealed that the spectral dependences of the Faraday and Kerr effects for ion-synthesized cobalt nanoparticles differ substantially from those for continuous cobalt films due to the localized excitations of free electrons in the nanoparticles.

Magnetic linear dichroism in FeBO3

Abstract Magnetic linear dichroism (MLD) and absorption spectra of FeBO 3 have been investigated in the region of the transition 6 A 1g → 4 E g , 4 A 1g ( 4 G) in the temperature range 103–346 K. It has been shown that MLD on the transition 6 A 1g → 4 E g is due to the exciton-magnon absorption mechanism. Jahn-Teller splitting of the 6 A 1g → 4 E g transition is observed in the MLD spectrum.

Magnetic circular dichroism and optical absorption in TmAl3(BO3)4

The polarized spectra of absorption and magnetic circular dichroism in a TmAl3(BO3)4 single crystal are studied in the region of 3H6 → 3F4, 3H6 → 3F3, and 3H6 → 3F2 electronic transitions in the Tm3+ ion. The structure of the spectra is interpreted qualitatively. It is shown that the magnetic circular dichroism of the 3H6 → 3F4 transition is determined by the contribution from the splitting of the ground state, whereas the magnetic circular dichroism of the 3H6 → 3F3 transition is governed by the contribution from the splitting of an excited state in a trigonal crystal field.