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 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.     

Magnetic and magneto-optical properties of Co-P films prepared by chemical deposition

Features in the formation of chemically deposited polycrystalline Co-P films with thicknesses of a few nanometers are established by analyzing film surface morphology and variation in the film magnetization. It is shown that in the thickness range below 30 nm the polar Kerr effect value θ_K changes nonmonotonically and depends on a wavelength of the incident light. For the films thicker than 30 nm, this value depends weakly on both the thickness and the wavelength. These features in the θ_K behavior are attributed to the Faraday effect, which is revealed at small thicknesses upon light reflection from the lower surface of a magnetic layer. It is found that the Faraday effect in the Co-P films exceeds that in the Co films by a factor of more than two. This effect is assumed to be caused by the presence of a Pd underlayer in the samples under study.     

Magnetic aftereffect in Co-P trilayer films

This paper reports on the results of experimental investigations of the magnetic properties of a trilayer system that consists of high-coercive polycrystalline and low-coercive amorphous magnetic Co-P layers and a nonmagnetic amorphous Ni-P interlayer. It has been established that the coercive force and the bias field of the hysteresis loop of the low-coercive layer undergo anomalous changes in the range of small thicknesses of the hard magnetic layer. In the same range of thicknesses, a magnetic aftereffect is found to manifest itself, which is unusual for this type of magnetic structures. The observed features are associated primarily with the kinetics of formation of a crystal structure of the high-coercive layer.     

Optical and magnetooptical properties of Co-doped YIG films

Conclusions Analysis of cobalt contributions to the Faraday rotation spectra in the series of (YCa)₃(FeCoGe)₅O₁₂ garnet films enabled us to distinguish between single contributions of Co²⁺ and Co³ ions in tetrahedral sites. It appeared that even the high counterdopes of calcium do not suppress the occurrence of tetrahedral Co²⁺ ions, although their concentration is greatly reduced in comparison with the original samples not containing any Ca. Noteworthy is also a rather high content of tetrahedral Co³⁺ in the samples not containing calcium even in cases when Ge content exceeds that of Co ions.     

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.     

Hard magnetic properties of sputtered Co and Co-P films

Both magnetic properties and microstructure of sputtered Co and Co-4.8 wt% P films ( ≈ 3000 Å) deposited near room temperature are studied as a function of Ar pressure P_Ar ranging from 4×10^-3 to 1.4×10^-1 Torr. The coercive force H_c of the film is a strong function of P_Ar. The coercive force of Co increases from 25 to 270 Oe with increasing P_Ar. With an addition of phosphorus in Co, H_c increases substantially. At high P_Ar ( ≈ 1×10^-1 Torr), a high H_c of 700 Oe and a low squareness of 0.58 are obtained. From observation of the microstructure, it is concluded that the structure of columns is responsible for the high H_c and the low squareness.     

Magnetic and magnetooptical properties of ferromagnetic semiconductor GaN : Cr

Magnetic and magnetooptical properties of the Cr-doped GaN layers have been investigated in the temperature range 50–400 K. A high saturation magnetization of 25 G has been observed in the obtained material. Spectra of the magnetooptical transversal Kerr effect have revealed strong magnetic response in the energy range less than 3.0 eV due to the appearance of new spin-polarization states in the band gap of GaN upon Cr doping.     

Effect of annealing on the magnetic and magnetooptical properties of Ni films

The magnetic and magnetooptical properties of 50-to 200-nm-thick Ni films, both as-deposited and annealed at T_ann = 300, 400, or 500°C, were studied. Volume and near-surface hysteresis loops were measured with a vibrating-sample magnetometer (VSM) and with the use of the transverse Kerr effect (TKE). The annealing temperature was found to exert a strong effect on the magnetic characteristics of the samples under study. It was established, in particular, that the coercivity H _C of Ni films increases and the remanent magnetization decreases with increasing annealing temperature. The observed dependences of the magnetic properties of the films on film thickness and annealing temperature are explained as being due to microstructural characteristics of the samples. It was found that, while TKE spectra obtained in the incident-photon energy region from 1.5 to 6 eV have the same shape for all the Ni films studied, the magnitude of the TKE decreases with increasing T_ann. This experimental observation is accounted for by the decreased saturation magnetization of the annealed films.     

Thermal properties of manganese-doped ZnO polycrystalline films

The thermal conductivity and heat capacity of manganese-doped zinc oxide polycrystals have been studied in the temperature range 30–300 K. A substantial influence of the secondary phase or MnO clusters formed as a result of doping on the temperature dependences of thermophysical properties of polycrystalline zinc oxide films has been shown.     

Transport and dielectric properties of thin polycrystalline CoO films

Transport and dielectric properties of polycrystalline CoO films were studied as functions of the applied field, frequency and temperature. TheI–V plots showed that the Poole-Frenkel field emission mechanism is responsible for conduction at fields>10⁵ V/cm. The ac conductivity σ(ω), the imaginary part of the dielectric constantε ₂, and tan δ plots as functions of frequency revealed three dispersion regions. The σ(ω) andε ₂ frequency dependence indicates a non-adiabatic hopping of charge carriers at low frequencies and adiabatic hopping at high frequencies. The activation energy of a dielectric oscillator is 0.15 eV. Work supported by the Office of Naval Research.     

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 properties of polycrystalline films of CoCr2O4 and CoFe0.5Cr1.5O4 multiferroics

This paper reports on the first study of the magnetic properties of polycrystalline films of CoCr₂O₄ and CoFe_0.5Cr_1.5O₄ multiferroics. The study covered, in particular, magnetization reversal curves and temperature dependences of the magnetization at temperatures ranging from 4.2 to 300 K in magnetic fields of up to 10 kOe. It has been shown that the Curie temperature and the pattern of the temperature dependence of the magnetization depend on the cation composition of the multiferroic. The temperature dependence of the magnetization of polycrystalline CoCr₂O₄ films has revealed an anomaly in the temperature range 10–70 K.     

Magnetic properties of ErN films

We report a magnetization study of stoichiometric ErN nanocrystalline films grown on Si and protected by a GaN passivating layer. According to the temperature dependence of the resistivity the films are heavily doped semiconductors. Above 100 K the magnetization data fit well to a Curie-Weiss behavior with a moment expected within the free-ion Er³⁺ multiplet. Below 50 K the Curie-Weiss plot steepens to an effective moment corresponding to that in the crystal-field determined quartet ground state, and develops a clear paramagnetic Curie-Weiss temperature of about 4.5 K. Zero-field- and field-cooled magnetization curves and the AC susceptibility firmly establish a ferromagnetic ground state within that multiplet below a Curie temperature of . Due to the (1 1 1) texture of the film the comparison between the magnetization behavior, when the field is applied parallel and perpendicular to the film plane, gives new information about the magnetic structure. An arrangement of the moments according to the model derived from neutron diffraction for bulk HoN is strongly suggested.     

Anomalies of magnetooptical diffraction in ferrite-garnet films

Experimental magnetooptical diffraction spectra produced by the band domain sructure in an epitaxial ferrite-garnet film are described. Asymmetry of the optical field in symmetric maxima is observed when a laser beam is normally incident on the sample. Analysis of the experimental data shows that the factors responsible for disrupting the symmetry of the magnetooptical diffraction spectrum include the inclination of the domain walls and inequality of the Fresnel coefficients fors andp polarizations of the incident radiation. Ul'yanovsk State Unviersyt. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 68–71, September, 1997.     

Magnetic annealing in electrodeposited Co-P amorphous alloys

The different diffusion processes that occur in electrodeposited Co-P amorphous alloys when they are subjected to magnetic annealing at different temperatures are studied by Coercive field measurements. Different processes are identified with different activation energies: 0.19 eV (stress relaxation): 0.75 eV (directional order); 2.9 eV (crystallization process). The low value of the activation energy for the first mechanism is identified with the diffusion of H, and that of the second with the diffusion of P.     

The photoelectric properties of polycrystalline films of gallium arsenide

Certain photoelectric properties of polycrystalline films of gallium arsenide at room temperature obtained by a gas deposition method are studied. It is found that film specimens of GaAs have much greater photosensitivity than the solid material for the same current carrier density.The barrier theory of conductivity is invoked in order to explain the relationships observed.     

Magnetic properties and application of nanocomposite films

Some peculiar properties of magnetic nanocomposite films have been considered. It is shown that the physical limit of practical application of these materials, determined by their superparamagnetic transition, can be overcome using the effects of magnetic and exchange interactions between nanoparticles.