J.M. Desvignes

Magnetic and magneto-optical properties of a cerium YIG single crystal

The magnetization and 1.15 μm wavelength Faraday rotation of Ce x Y 3-x Fe 5 O 12 (Ce x = YIG) with x = 0.06 single crystals have been measured. For two directions of the applied magnetic field (H [111] and H [110]) up to 50 kOe, the isothermal magnetization curves are identical to that of pure YIG between 4.2 and 300 K. On the other hand, the Faraday rotation (F.R.) in a maximum field of 20 kOe parallel to the [111] direction is always negative (with respect to the positive FR of YIG) and strongly enhanced when the temperature is lowered from 300 to 77 K. These interesting magnetooptical properties are associated to the presence of Ce3+ions in the samples.

FMR linewidth of barium hexaferrite at millimeter wavelengths

Measurements are reported on the magnetostatic and dielectric resonances of samples of barium hexaferrite single crystals in the millimeter wavelength range. The behavior of these resonances versus frequency and temperature leads to the conclusion that the contribution of the intrinsic loss to the FMR linewidth is about ten times higher than for YIG.

Coupling and phase matching coefficients in a magneto-optical TE-TM mode converter

Abstract TE-TM mode conversion, in magneto-optic guides for integrated optics, requires TE-TM mode overlap and phasematching. This two properties are analyzed with circular and linear magnetic birefringence dependence. In application an experimental 95% TE-TM mode conversion efficiency is presented for an uniform longitudinal magnetization.

Correlation of GMR with texture and interfacial roughness in optimized rf sputtering deposited Co/Cu multilayers

Abstract The objectives of the present work were two fold: first to obtain the highest giant magnetoresistance (GMR) ratio in Co/Cu multilayers grown from the unusual process of rf diode sputtering and second, to investigate in detail correlation between GMR and texture and the interfacial roughness deduced from X-ray diffraction and AFM, respectively. Different interface structures have been induced from the change of the sputtering parameters (sputtering argon gas pressure P Ar ) which gave the optimal rf sputtering conditions for high GMR. From different results it is concluded that the most important parameter is interface roughness which induces a strong effect on both the GMR and the resistivity of the superlattice. A change in the t 2 Co dependence of the reciprocal resistance near t Co = 25 A is attributed to an increase of the effect of the layer roughness when the t Co is going from mesoscopic ( t Co > 25 A) to nanoscopic scale ( t Co

Correlation of spontaneous Faraday rotation with sublittices magnetization in some rare earth garnet RIG (R = Tb, Dy, Ho, Er)

Abstract The Faraday rotation of iron garnets originates from electric and magnetic dipole contributions of magnetic sublattices. Previous analysis where electric dipole coefficients were taken temperature independent fail. Assuming same Fe 3+ ion contributions as in YIG, the electric dipole coefficient of the rare earth is strongly temperature dependent.

Magneto‐optic and magnetic properties of praseodymium substituted garnets

On PrxY3−x Fe5O12 substituted garnets magnetic magnetization and Faraday rotation (φF) have been measured in the 4.2–300 K temperature range with magnetic field applied parallel to the ‖111‖ direction. The wavelength varies from 1 to 1.3 μm and three Pr3+ concentrations 1.10, 0.70, and 0.35 were studied. At 4.2 K, the spontaneous magnetic moment attributed to one Pr3 ion is deduced from the Neel model to be (1.55±0.15) μB as previously found in polycrystalline samples. At 1.15 μm wavelength the contribution of the Pr sublattice to φF is determined assuming the contribution of the Fe3+ ions equal to the YIG experiemental data. φF induced by one Pr3+ ion is found identical in the three ferrites of various concentrations for T≳90 K. Below this temperature, discrepencies of about 15% between the Pr3+ contributions to φF were evaluated. Characteristic values are obtained: −(475±25) deg cm−1 at 300 K, −(700±50) deg cm−1 at 90 K, −(1800±200) deg cm−1 at 9 K. Such a behavior which shows the one ion model to be va...

High magnetic field properties of mixed terbium-yttrium ferrite garnets

Magnetization measurements in d.c. magnetic fields up to 180 kOe have been performed on polycrystalline specimens and on single crystals of mixed terbium-yttrium iron garnets: TbxY3−xFe5O12 in the 4.2–300 K temperature range. On polycrystals (x=2.5; 2; 1; 0.37) the concentration dependence of both compensation point and spontaneous magnetization has been determined. In the single crystals (x=2; 1; 0.37) a strong magnetic anisotropy has been observed with a change of the easy direction of magnetization from [111] to [100] whenx decreases; abrupt field-induced transitions have been observed at low temperatures when the external field is applied along the [100] direction.

Faraday rotation in single crystal erbium iron garnet

Abstract Measurements of the Faraday rotation of ErIG, Er 3 Fe 5 O 12 , have been performed in the 4.2–300 K temperature range in magnetic field up to 20 kOe applied along the [111] direction and at 1.15 μm wavelength. The results are analysed under the assumption that the contribution of the Fe 3+ ions to the total Faraday rotation is the same as that of YIG, Y 3 Fe 5 O 12 . The temperature and field dependences of the contribution of the Er 3+ ions are deduced. Both magnetic and electric dipole contributions of the Er 3+ ions are calculated; the electric dipole coefficient C e is found to present a linear temperature dependence between 30–300 K. The temperature dependence of the Faraday rotation susceptibility differs strongly from that of the magnetic susceptibility.

Amorphization and recrystallization of yttrium iron garnet under swift heavy ion beams

The room-temperature dc conductivity is used to monitor the damage and structural modifications induced by swift heavy ion irradiations in yttrium iron garnet (Y3Fe5O12 or YIG) epitaxial layers doped with calcium (CaYIG) or silicon (SiYIG), with a variable conductivity due to a variable degree of compensation, and amorphous YIG layers. Irradiations are performed with heavy ions in the 0.8–6 MeV amu−1 energy range, in the electronic slowing down regime, with an electronic stopping power ranging between 7 and 41 MeV μm−1 above the amorphous track formation threshold (4.5 MeV μm−1) in this low-ion velocity range. A conductivity decrease versus ion fluence is found in the case of the high-conductivity uncompensated epilayers whereas an increase occurs for the low-conductivity compensated ones, either p-type (CaYIG) or n-type (SiYIG). These results are discussed by considering the competing effects of disorder on the carrier density and mobility in the case of compensated and uncompensated semiconductors. In b...

Faraday rotation of bismuth substituted dysprosium iron garnets

The spontaneous magnetization and the Faraday rotation FR, or [110]-oriented single crystal of composition Bi/sub x/Tb/sub 3-x/Fe/sub 5/O/sub 12/ with x=0.60 have been investigated as a function of temperature and compared with bismuth-free terbium iron-garnet. The experimental data, obtained at 1150 nm wavelength in the 10-300 K temperature range, are discussed in terms of electric and magnetic dipole transitions within the three magnetic sublattices. Assuming that the contribution of the Fe/sup 3+/ ions to FR is the same as bismuth-substituted yttrium iron garnet (for identical Bi content), the contribution to FR of the Tb dodecahedral ion exhibits a strong reduction induced by the bismuth incorporation. A strong temperature variation of the 1st order electric dipole coefficient for the rare earth is found; in a first approximation, this coefficient presents a linear temperature dependence in the 100-300 K temperature range as previously observed in the pure TbIG. >