E.A. Gan'shina

Surface-plasmon-induced enhancement of magneto-optical Kerr effect in all-nickel subwavelength nanogratings

Enhancement of transversal magneto-optical Kerr effect (TKE) is controlled experimentally in magnetoplasmonic subwavelength nanogratings made of nickel films by resonant excitation of surface plasmon-polaritons (SPPs). Almost one order of magnitude increase of the TKE value is observed in the spectral range of Wood’s anomaly corresponding to the fulfillment of the phase-matching conditions for SPP excitation.

Optical and magneto-optical spectra of magnetic granular alloys

We present the results of the experimental and theoretical investigation of the optical and magneto-optical (MO) spectra of magnetic granular films (Co70Fe30)xAg1−x, CoxAg1−x, in the energy range 0.5-4.0 eV of incident light. The MO properties were investigated in the geometry of transverse Kerr effect. The MO spectra of granular alloys are quite different from the spectra of homogeneous films. The amplitude of Kerr signal and the MO spectra profile depend on the granular and matrix material, the concentration and the shape of the grains and the annealing temperature. We interpret the obtained spectra in the framework of the effective medium approximation that allows to make some conclusions about ferromagnetic particle concentration and their shape.

Giant change in infrared light transmission in La0.67Ca0.33MnO3 film near the Curie temperature

Yu. P. Sukhorukov,, E. A. Gan’shina, B. I. Belevtsev, N. N. Loshkareva, A. N. Vinogradov, K. D. D. Rathnayaka, A. Parasiris, D. G. Naugle Institute of Metal Physics, Ural Division of the Russian Academy of Sciences, 620219 Ekaterinburg, Russia Physics Department, Moscow State University, 119899, Moscow, Russia B. Verkin Institute for Low Temperature Physics & Engineering, Ukrainian Academy of Sciences, Kharkov, 61103, Ukraine Department of Physics, Texas A&M University, College Station, TX 77843-4242, USATransport, magnetic, magneto-optical (Kerr effect) and optical (light absorption) properties have been studied in an oriented polycrystalline La0.67Ca0.33MnO3 film which shows colossal magnetoresistance. The correlations between these properties are presented. A giant change in infrared light transmission (more than a thousand-fold decrease) is observed on crossing the Curie temperature (about 270 K) from high to low temperature. Large changes in transmittance in a magnetic field were observed as well. The giant changes in transmittance and the large magnetotransmittance can be used for development of IR optoelectronic devices controlled by thermal and magnetic fields. Required material characteristics of doped manganites for these devices are discussed.

Giant magnetorefractive effect in La{sub 0.7}Ca{sub 0.3}MnO{sub 3} films

Complex experimental investigations of the structural, optical, and magneto-optical properties (magnetotransmission, magnetoreflection, and transversal Kerr effect, as well as the magnetoresistance, of La0.7Ca0.3MnO3 epitaxial films indicate that magnetoreflection and magnetotransmission in manganite films can reach giant values and depend strongly on the magnetic and charge homogeneity of the films, their thickness, and spectral range under investigation. It has been shown that the optical enhancement of the magnetorefractive effect occurs in thin films as compared to manganite crystals. In the region of the minimum of the reflectance near the first phonon band, the resonance-like magnetorefractive effect has been observed, which is accompanied by change of the sign of the magnetoreflection. A model based on the theory of the magnetorefractive effect has been proposed to qualitatively explain this behavior.

Low-temperature irreversible structural relaxation of amorphous metallic alloys

Abstract New phenomena, irreversible changes of the main physical properties due to the transition of amorphous metallic alloys into novel metastable state after low-temperature treatment has been observed for the first time. Two-step model is proposed including breaking of the atomic bonds in associates by thermo-elastic stresses as the first step and low-temperature structural relaxation caused by elastic stress waves as the second step.

Anisotropy of the circular magneto-optics of orthoferrites: A theoretical consideration on the basis of the charge-transfer transitions and exchange-relativistic interactions concept

Abstract A theoretical analysis of the magneto-optic effects (MOE) in the holmium orthoferrite, HoFeO 3 , in the 2–6 eV region is made in the framework of oxygen-to-iron charge-transfer transitions in octahedral FeO 6 9− complexes. The necessity of taking into account a new type of interactions—the exchange-relativistic ones—in order to explain the origin and anisotropy of MOE in orthoferrites and other weak ferromagnets is shown and the characteristic magnitude of these interactions estimated. Effective exchange-relativistic orbital fields—analogues of the Dzyaloshinsky spin field—reach magnitude ≈ 100 T in orthoferrites.

The local environment of cobalt in amorphous, polycrystalline and epitaxial anatase TiO2:Co films produced by cobalt ion implantation

Amorphous, polycrystalline anatase and epitaxial anatase TiO2 films have been implanted with 5 at. % Co+. The magnetic and structural properties of different microstructures of TiO2:Co, along with the local coordination of the implanted Co atoms within the host lattice are investigated. In amorphous TiO2:Co film, Co atoms are in the (II) oxidation state with a complex coordination and exhibit a paramagnetic response. However, for the TiO2:Co epitaxial and polycrystalline anatase films, Co atoms have a distorted octahedral (II) oxygen coordination assigned to a substitutional environment with traces of metallic Co clusters, which gives a rise to a superparamagnetic behavior. Despite the incorporation of the implanted atoms into the host lattice, high temperature ferromagnetism is absent in the films. On the other hand, it is found that the concentration and size of the implantation-induced nanoclusters and the magnetic properties of TiO2:Co films have a strong dependency on the initial microstructure of Ti...

Defect-induced high-temperature ferromagnetism in Si1-xMnx(x???0.52?0.55) alloys

We present a comparative study of the anomalous Hall effect (AHE) and of the transverse Kerr effect (TKE) in the nonstoichiometric alloys. The data on AHE and TKE are consistent with each other and clearly indicate the intrinsic above room-temperature ferromagnetic order in the studied samples. We argue that this order is not produced by the phase segregation effects, but rather has a global character, while even a small level of the nonstoichiometry in alloys drastically changes their magnetic, electrical, optical and magneto-optical properties as compared to those of the stoichiometric manganese monosilicide MnSi. We propose a qualitative explanation of the obtained experimental results in the frame of the model of defect-induced ferromagnetic order using the first-principles calculations of the electronic and magnetic structure of the system.

Magnetostatic properties of heterogeneous Co-based amorphous/crystalline phases

Abstract Using the magneto-optical Kerr effect, magnetic hysteresis loops are measured on annealed amorphous Co 66 Fe 4 B 15 Si 15 samples, to characterize the magnetostatic properties of the heterogeneous crystalline/amorphous phases. A gradual change, on microscale inhomogeneous, change of the magnetic properties with respect to thickness is revealed on HCP-Co, FCC-Co crystalline phases near the surface. The inner amorphous phase exhibits an irregular variation of the local magnetic properties, presumably due to the occurrence and distribution of microcrystallites. The effective field, exerted by the crystalline layer on the amorphous phase, is opposite to the surface magnetization, indicating that there is an antiferromagnetic coupling between surface and inner amorphous phases.

Transverse Kerr effect in the (La1-xPrx)0.7Ca0.3MnO3 ceramics

Magneto-optical properties were measured for (La1-x Prx )0.7 Ca0.3 MnO3 (x = 0, 0.25, 0.5, 0.75, 1) ceramic solid solutions, including temperature, magnetic field, oxygen isotope content and spectral dependences of the transverse Kerr effect (TKE). The TKE spectra after the transition to the ferromagnetic metallic state depend only weakly on the substitution of La for Pr as long as x 0.5. A surface magnetism contribution results in a TKE peak near TC but it can be suppressed by magnetic field or a long-time annealing. A significant oxygen isotope effect is observed for all compositions, being critical for x = 0.75. Hysteresis phenomena of two different types were observed in the temperature dependences of TKE. The first type, related to the ferromagnetic fluctuations, was found for x 0.5 (TKE is larger on cooling). The second type was related to the magnetically inhomogeneous state for x = 0.75 and 1 (TKE is larger on heating). The hysteretic variations in the magneto-optical spectrum of (La0.25 Pr0.75 )0.7 Ca0.3 MnO3 are referred to the possible charge carrier redistribution between the incipient ferromagnetic component and the charge ordered antiferromagnetic component.