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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

Garnet films of the series (Bi,Lu)3(Fe,Mg)5O12, with Bi contents of 0.85/f.u., have been investigated using microwave techniques. The samples were 1.7–10 μm thick, and were grown under different conditions. The uniaxial anisotropy and the resonance linewidths were evaluated over the temperature range 4.2–300 K. The magnetostatic wave propagation losses in the interval 3–6 GHz were measured and correlated with the resonance linewidths and the sample growth conditions. For these samples the resonance linewidth maxima occurred at about 50 K. The minima of the propagation loss and the resonance linewidth were obtained for the film growth velocity υ = 0.88 μm/min. The processes of microwave soliton formation and propagation have been observed experimentally in these Bi-doped garnet films. Under the continuous-wave regime modulation instability was observed.

The garnet YIG:Co films have been investigated within the temperature range 10–300 K. Torque magnetometry study showed the temperature-induced spin-reorientation phase transitions. Using the Faraday effect, magnetic domain structures were visualized by optical microscope and analyzed by digital image processing technique. Temperature- and magnetic-field-induced transitions between phases with in-plane and out-of-plane magnetization were studied by the magneto-optical technique.

The effect of linearly polarized light on the metamagnetic phase transition in the antiferromagnetic Ca 3 Mn 2 Ge 3 O 12 garnet was studied. The photoinduced change of the transition field has been found. The observed effect is related to the magnetic moment that arises in this antiferromagnetic under illumination.

The correlation between the giant magnetoresistance Δ R / R , at the first maximum of the oscillating thickness dependence of the magnetoresistance (MR), and the structural and magnetic parameters has been investigated in (Co/Cu) multilayers (ML) deposited by the unusual RF sputtering method. Different textures and interface roughnesses have been induced from magnetic (Fe, Co) and non-magnetic (Cu, Al, Ta, Cr) buffers. The MR is independent of the ML texture and grain size but presents a strong correlation with the interface as deduced from small and large angle XRD and AFM. In high roughness ML the evolution, under increasing applied field, of Δ R / R versus ( M / M s ) 2 presents a strong deviation from a standard linear dependence. Such a deviation is attributed to the presence of Co granules in the Cu or/ and the buffer matrices when strong interface disorder is induced in the samples.

Domain wall resonance (DWR) has been investigated in a parallel stripe lattice using a new high sensitivity DWR excitation and detection technique. Experiments were performed on garnets with pure uniaxial and orthorhombic anisotropy. A strong dependence of the DWR frequency on the intrinsic medium parameters, such as the saturation magnetization and the anisotropy constants, was observed. The influence on the domain oscillation frequency of an in-plane field applied parallel and perpendicular to the wall plane was analyzed and the corresponding changes of the wall mass and restoring constant was determined in (111)- and (110)-oriented garnet films.

Ferromagnetic resonance has been studied in Y 3− z Ca z Fe 5− x-y Co x Ge y O 12 films grown on the (001) plane of a GGG substrate. Temperature-induced spin-reorientation phase transitions were observed. On cooling the sample, the easy magnetization axes orientations changed from directions near [111] to [100], and the [001] direction had the lowest energy. The FMR signal was practically non-measurable below 60 and 120 K when the magnetic field was applied along the [110] and [100] axes, respectively.

A quantitative investigation of domain structure shape memory effect in YIG: Co,Ge,Ca films, grown by LPE, is reported. Domain images were registered in an optical microscope using Faraday effect. A special digital image processing technique was used. Both memory ‘creation’ and ‘erasing’ were studied after the sample had been put under the influence of different factors, which caused domain destruction. This phenomenon was explained taking into consideration magnetization induced anisotropy and non-colinear magnetization directions in neighboring domains.

Polarized light induced ‘soft’ and ‘rigid’ linear dichroism was found in YIG: Co films. The ‘rigid’ photo-induced dichroism seems to be connected with Co 2+ in the tetrahedral side. The effect of optical anisotropy memory was observed after heating and recooling of the sample.

Observation of the reflection of magnetostatic waves from a periodic grating, fabricated by means of laser annealing in a Ga-doped garnet film is reported. The behavior of the peaks of reflectivity is interpreted in terms of the phase matching condition.

Faraday Rotation (FR) measurements performed on single crystal terbium-yttrium iron garnets (Tb 0.35 Y 2.35 Fe 5 O 12 ) are reported at 1.15 μm wavelength in the temperature range 6–300 K, under magnetic field up to 20 kOe applied along the [111] and [100] directions. The spontaneous FR is isotropic while the 'FR susceptibilities are anisotropic at low temperature, anisotropy which originates mainly from spin reorientation transitions. To analyse the terbium contribution to FR, the Fe 3+ contribution is identified to the YIG data: the electric dipole contribution of the Tb 3+ ion is found well described by the ‘one-ion’ model.

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.

The room temperature crystal structure of BaZnFe 6 O 11 Y-type ferrite is refined from X-ray single crystal data. This compound is trigonal (space group R 3 m); expressed in the hexagonal axes, the cell parameters are: a = 5.875(1) A and c = 43.571(6) A and there are 6 formula units in this nonprimitive cell. The location of the Zn 2+ cation among the six sublattices of the structure is given: this cation lies in the only tetrahedral sites with a marked preference for the S-block ones (71%). A complete description of the structure is done and the superexchange interactions paths are given.

After being annealed at different equilibrium temperatures 1125⩾ T e ⩽1473 K, Ga-substituted YIG films were quenched and the change of the magnetic properties of the material (4π M s , K u ) and the bubble parameters (field stability range, diameter, collapse field, characteristic length, wall energy) associated with the cation migration induced by the thermal treatment were determined. The results are discussed.

Measurements were made on Sb doped YIG in order to understand the dopant influence on the magnetooptical effects in iron garnets. The results are analyzed to determine the character of the symmetry of active centers, which are responsible for these effects.

The linear magnetooptical effect was used to examine the magnetic symmetry of the tetragonal antiferromagnet garnet MnGeG having a complex multisublattice structure. The properties of the magnetic field ( H ‖ C 4 ) induced linear birefringence and dichroism for light k ‖ C 4 provide evidence of the group 4 /m being a MnGeG magnetic group.

On a single crystal of erbium ion garnet (ErIG), magnetization curves M ( H ) were measured in H ⩽ 150 kOe at temperature 1.4 K ⩽ T ⩽ 300 K. At low temperatures, [100] is the easy direction. Below T comp (80K), the ferrite magnetization M ( H ) presents a nonlinear evolution up to 150 kOe which is not found for T > T comp .