Magnetic and magnetooptical properties of multilayer ferromagnet-semiconductor nanostructures

The magnetic and magnetooptical properties of spin-tunneling multilayer permalloy-silicon carbide nanoheterostructures deposited by rf sputtering have been studied. Magnetometric and magnetooptical methods are used to show that the magnetic-semiconducting nanostructures have a complex magnetic structure and to track the evolution of the magnetic properties of these structures as functions of the magnetizing field and the thickness and sequence order of ferromagnetic and semiconducting layers in them. The induction response and the field and orientation dependences of the transversal Kerr effect are found to have anomalies. The experimental results are interpreted under the assumption that there is exchange interaction between the ferromagnetic and semiconducting layers through a thin magnetically ordered transition layer formed inside the interface.     

Magnetic and magnetooptical properties of nanothick polycrystalline Co-P films

Features of the formation of chemically deposited polycrystalline Co-P films with nanometer thicknesses are established by magnetic measurements and analysis of film surface morphology. It is found that the specific value of the magnetooptical Faraday effect in Co-P films exceeds that in Co films by a factor of more than two. This is attributed to the magnetic polarization of a Pd underlayer. It is shown the Kerr effect in Co films is negligibly influenced by the embedding of phosphorus.     

Theory of magnetooptical effects in ferromagnetic metals

Magnetooptical effects in ferromagnetic metals have been studied by the Kohn-Luttinger method, by means of electron scattering by impurity centers. There is a discussion of the more general case, in which the external agent has both a frequency and a wave vector. Solution of the corresponding kinetic equation with an account of the diffusion term reveals the symmetric and antisymmetric parts of the complex average velocity, valid for both high and low frequencies.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 12, No. 7, pp. 47–50, July, 1969.     

Magnetic and magnetooptical properties of Gd-Co-Si films of various thickness

The magnetic, optical, and magnetooptical properties of amorphous Gd-Co-Si films of various thickness are investigated. It is shown that the perpendicular component of anisotropy in the films is preserved to very small thicknesses, down to 0.005 m. The character of the thickness dependence of the anisotropy constant is analyzed and compared with the behavior expected according to a simple theoretical model which assumes that the perpendicular anisotropy originates from the microstructure. It is concluded that the probable source of the perpendicular anisotropy in these materials is the anisotropic distribution of atom pairs.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 70–75, January, 1986.     

Theory of magnetooptical effects in ferromagnetic nickel

A theory is developed for magnetooptical effects in ferromagnetic nickel with allowance for the topology of the Fermi surface at low temperatures, when the carriers are scattered on ionized impurity centers. The contribution to the frequency conductivity tensor due to the anisotropy of the Fermi surfaces of nickel is found and it is shown that this contribution in the first approximation of perturbation theory reduces to a decrease of the tensor . An estimate is made of the influence of the density of states of nickel on the anomalous frequency-dependent Hall current and a study is also made of the case of low and high frequencies, when, respectively, ^{2 2} « 1 and ^{2 2} » 1.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 29–33, May, 1972.     

Theory of magnetooptical effects in thin ferromagnetic films

A systematic theory is derived for the anomalous magnetooptical effects in thin ferromagnetic films for the more general case in which conduction electrons are scattered by both phonons and impurities. The Kohn-Luttinger density-matrix method is used to find the tensor for the complex transverse conductivity, which is linear in the spin-orbit interaction and can be used to find the magnetooptical parameter. The temperature dependences of the real and imaginary parts of the conductivity tensor are found for high temperatures.     

Magnetic coupling in ferromagnetic semiconductor GaMnAs/AlGaMnAs bilayer devices

We carefully investigated the ferromagnetic coupling in the as-grown and annealed ferromagnetic semiconductor GaMnAs/AlGaMnAs bilayer devices. We observed that the magnetic interaction between the two layers strongly affects the magnetoresistance of the GaMnAs layer with applying the out of plane magnetic field. After low temperature annealing, the magnetic easy axis of the AlGaMnAs layer switches from out of plane into in-plane and the interlayer coupling efficiency is reduced from up to 0.6 to less than 0.4. However, the magnetic coupling penetration depth for the annealed device is twice that of the as-grown bilayer device.     

Magnetic properties for heterogeneous weakly ferromagnetic alloys

Using the Landau theory of phase transitions, Arrott plots, the high field and the paramagnetic susceptibility and the magnetization of heterogeneous weakly ferromagnetic alloys are calculated analytically for a simple model for the heterogeneity.     

Magnetic and structural properties of Fe ion-implanted GaN

The magnetic and structural properties of Fe ion-implanted GaN was investigated by various measurements. XRD results did not show any peaks associated with second phase formation. The magnetization curve at 5 K showed ferromagnetic behavior for 900 °C-annealed sample. In zero-field-cooled (ZFC) and field-cooled (FC) magnetization measurements, the irreversibility and a cusp-like behavior of the ZFC curve were observed for 900 °C-annealed sample. These behaviors are typically observed in superparamagnetic or spin glass phase. While the temperature dependence magnetization of 800 °C-annealed sample showed non-Brillouin-like curve and it is not exhibited ferromagnetic hysteresis at 5 K. In XPS measurement, the coexistence of metallic Fe (Fe⁰) and Fe–N bond (Fe²⁺ and Fe³⁺) for Fe 2p core level spectra is observed in as-implanted sample. But 700–900 °C-annealed samples showed only Fe–N bond (Fe²⁺ and Fe³⁺) spectra. For Ga 3d core level spectra only Ga–N bonds showed for as implanted with 700–900 °C-annealed samples. From XPS results, it could be explained that magnetic property of our films originated from FeN structures.     

Magnetic and magnetooptical properties of Au/Cu-wedge/15-Å-NiFe sandwiches

The results of an investigation of the magnetic and magnetooptical properties of Au/Cu-wedge/15-Å-NiFe sandwiches are reported. Oscillations of the equatorial Kerr effect as a function of the copper wedge thickness are observed. The period of these oscillations is found to be of the order of 5–6 Å. The experimentally observed oscillations of the equatorial Kerr effect are attributed to a quantum size effect. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 1, 33–36 (10 January 1998)     

Magnetic and magnetooptical properties of polycrystalline films of La0.7Sr0.3MnO3

Magnetic circular dichroism (MCD) is studied in comparison with the magnetic behavior of polycrystalline films of La_0.7Sr_0.3MnO₃ (LSMO) deposited on a single crystal of zirconium oxide stabilized by yttrium (YSZ). It is found that the bands observed in MCD spectra are characterized by different temperature dependences.     

Magnetic properties of CrPd alloys

Magnetic susceptibility, resistivity, and neutron diffraction measurements have been obtained for a series of CrPd alloys containing up to 3 at.% Pd. The Néel temperature variation is irregular for a solute which is to the right of Cr in the periodic table.     

Magnetic polaron in a ferromagnetic semiconductor. A new self-consistent finite temperature solution

A complete self-consistent finite temperature theory of magnetic polaron states with damping in a ferromagnetic semiconductor is developed using the irreducible Green function (IGF) method.     

A note on the theory of magnetooptical phenomena in ferromagnetic metals

The ferromagnetic, frequency-sensitive Hall conductivity causing magnetooptical effects in ferromagnetic metals is investigated. Expressions are obtained for the symmetric and antisymmetric parts of the complex conductivity tensor. The temperature dependence of the frequency-sensitive complex conductivity at high temperature is found for the more general case when the conductivity electrons are scattered by both phonons and impurity centers.     

Co掺杂的ZnO室温铁磁半导体材料制备与磁性和光学特性研究

采用溶胶-凝胶法制备出具有室温铁磁性的Co掺杂的ZnO稀磁半导体材料. 通过对样品的结构、磁性和发光特性的研究发现,样品具有室温铁磁性,并发现其铁磁性源于磁性离子对ZnO中Zn离子的取代. 对不同温度制备的样品的磁性以及其发光特性的变化研究发现,样品的铁磁性与样品中锌间隙位（Zn_i）缺陷的密度有关. 关键词： ZnO 稀磁半导体 铁磁性     

Magnetic and structural properties of non-stoichiometric Ni-Mn-Ga ferromagnetic shape memory alloys

Structural and magnetic transition temperatures of ferromagnetic shape memory alloys present a strong dependence on slight departures from the stoichiometry, as does the mobility of twin boundaries responsible for the large magnetic field induced strains. In this work we study four non stoichiometric Ni-Mn-Ga polycrystalline alloys with compositions of 43–52 at.% nickel, excess manganese and deficient in gallium, and a single crystal of composition Ni₅₂Mn₂₆Ga₂₂. Those compounds are of technical interest due to the observed large room temperature magnetic field induced strains. Calorimetric and magnetic measurements determined the martensitic transition and Curie temperatures of the alloys (A_S = 331 K and T_Curie = 366 K for 52 at.% nickel alloy). Nickel defective alloys present a martensitic transition region broader than excess nickel ones. Neutron powder diffraction analysis confirmed orthorhombic martensitic structures for nickel defective alloys, and tetragonal for excess nickel ones. In the 52 atomic % nickel alloys case the crystallographic structure of the martensitic phase was also obtained on a single crystal with the same composition, trained to get a single variant in agreement with determined in the powder sample.