Solid State Phenomena Vols. 168-169

Abstract: A new way of considerable improvement of properties of soft magnetic alloys is offered. This way actually consists in the use of an ion beam treatment in the manufacturing technology for these alloys. Depending on the properties, which need improvement (magnetic softness or magnetostriction), the ion beam treatment is performed before or after a thermomagnetic treatment.

Abstract: In this paper we present the results of investigation of spiral dynamic domains of a highly anisotropic iron garnet film with a perpendicular anisotropy in magnetic field with a constant dimensional gradient. The experiment showed how the presence of gradient of constant field affects the main parameters of spiral dynamic domains – geometrical form, life time, amount of orbits.

Abstract: Analytical and numerical methods are used to study the process of motion of domain walls in an individual nanowire consisting of ferromagnetic crystallites with a chaotic crystallographic anisotropy. The influence of magnetostatic interaction on the motion is considered. The force profile of the domain wall pinning, caused by stochastic crystallographic anisotropy, is examined. The magnetization curve is analytically constructed and the coercive force is calculated. The Barkhausen jumps of domain walls are investigated. The result is verified by numerically modeling.

Abstract: Structure of magnetic heterogeneities of the 0-degree-domain-wall type in a thin film of a cubic ferromagnet with a uniaxial anisotropy induced along [011] is examined. Strict calculations of demagnetizing fields are shown to lead to quasibloch solutions with values of material parameters lying in certain ranges. Besides, the magnetization vector’s leaving the domain wall plane means the rotation of plane orientation by the angle π/4. The transition boundary between the described structures is found.

Abstract: Theoretical analysis of peculiarities of electric polarization arising on magnetic non – homogeneity in bilayered structure with interlayer antiferromagnetic coupling has been performed. It has been shown that the total electric polarization can be of the positive and of the negative sign or equal to zero depending on the relation between layers parameters. Electric polarization can be governed by applied magnetic field through magnetization processes occurring in a system; in its turn the electric field affects the distribution of magnetic moments.

Abstract: Laser deposition method was used for growing ferromagnetic semiconductor and half-metal compound layers. GaMnAs and InMnAs layers were grown by alternating laser ablation of solid targets (semiconductor and Mn) in hydrogen and arsine flow. The layers exhibited ferromagnetic properties (detected by Hall effect measurements) from 10 K to room temperature (for InMnAs). Half-metal compound layers were deposited by the techniques of reactive laser deposition (MnAs, MnP) and alternating laser deposition (MnSb). The half-metal layers exhibit ferromagnetism at temperatures up to 300 K.

Abstract: The remagnetization process and the distribution of magnetic moments in arrays of trilayer nanodisks Co(10 nm)/Pd(0.8 nm)/Co(10 nm) with diameters D = 200 and 400 nm were studied by the magnetooptical Kerr effect (MOKE) and magnetic force microscopy (MFM). It is shown that in the nanodisks with D = 200 nm the magnetisation reversal process can be carried out by the vortex states or one-domain configurations with the antiparallel orientation of moments in the adjacent ferromagnetic layers. In arrays of nanodisks with D = 400 nm the vortex states are formed only.

Abstract: This paper is devoted to the investigation of crystalline structure, surface morphology, magnetic anisotropy, coercive force and domain structure of spin-valves with a single and double MgO barrier layers. It is shown that domain structure and magnetization reversal are the same for both systems, but otherwise the behavior of tunnel magnetoresistance is different. The approach to control magnetic anisotropy in soft magnetic layer using temperature annealing is demonstrated. It makes these structures possible for new applications in nanoelectronics.

Abstract: FeNi films were deposited by DC magnetron sputtering at different Ar pressures. The structure and magnetic properties of the FeNi films are affected by the Ar pressure. Ferromagnetic resonance (FMR) measurements were done at a frequency of about 8.85 GHz. Both the value of resonance field and resonance line width show strong dependence on the Ar pressure: the lowest value of the resonance field and the narrowest resonance width correspond to the smallest argon pressure. Increase of the Ar pressure causes the films to have a significant perpendicular anisotropy with the easy axis pointing out of the plane. The magnetic properties and FMR were also studied for the [FeNi(170 nm)/Ti]n/FeNi(170 nm) (n = 1, 2, 5) structures prepared at the smallest Ar pressure. The FMR studies showed that the obtained multilayers are very robust: the value of the resonance field and resonance line width of the [FeNi/Ti]n/FeNi multilayers are very close to the corresponding values for the FeNi films.

Abstract: The surface morphology and magnetic properties of layered Ni-Ge films were investigated. The films surface has been shown to consist of the grains of 2 - 4 nm in height with the average radius of about 40-80 nm. Magnetization temperature dependences are different for FC and ZFC processes; in the latter case, the magnetization maximum is observed near the temperature Tm~50K. The exchange bias effect is observed at low temperatures. The results are explained by the formation of the antiferromagnetic phase in the interface between Ni and Ge layers due to the Ge and Ni mutual diffusion.