Free magnetization oscillations in garnet ferrite films with quasi-planar anisotropy

Free magnetization oscillations in garnet ferrite films with quasi-planar anisotropy was studied. The oscillations were excited by a pulse of an in-plane magnetic field. An analytic expression relating the oscillation frequency to the film parameters and the external magnetic field was derived; the expression is in good agreement with the experimental data. The planar anisotropy is shown to increase the free-oscillation damping.     

Inhomogeneous configurations of magnetization of ferromagnetic films with biaxial anisotropy

The system of the Landau-Lifshitz equations and magnetostatic equations for a ferromagnetic film with biaxial anisotropy and a Q-factor smaller than unity is reduced to a single scalar equation for the magnetostatic potential. Such a procedure is possible if the magnetization modulation scale in the sample considerably exceeds the characteristic magnetic length. The solutions to this equation describing inhomogeneous periodic magnetic configurations are obtained. The energy analysis of these configurations is carried out.     

Effect of noncrystallographic magnetic anisotropy on magnetization reversal in multilayer magnetic films

A study has been carried out of the magnetization of a layered system consisting of two exchange-coupled easy-axis ferromagnetic layers separated by a nonmagnetic spacer and having mutually perpendicular anisotropy axes. It is shown that the magnetization of such a system can undergo stepwise decrease with increasing magnetic field. The field dependence of the magnetization has a bifurcation point. The magnetization orientation can exhibit jumps in excess of 90° depending on the angle of magnetic-field orientation. Fiz. Tverd. Tela (St. Petersburg) 41, 660–664 (April 1999)     

Nonlinear oscillations of magnetization accompanying pulsed 90°-magnetization of garnet ferrite films with easy-plane anisotropy

Abstract Nonlinear oscillations of magnetization (with a fundamental harmonic frequency of ≈0.5 GHz) emerging during 90°-pulsed magnetization of garnet ferrite films with easy-plane anisotropy are studied. Analysis of longitudinal and transverse magnetization signals and of the magnetization vector hodograph plotted on their basis shows that the weak dependence of the oscillation intensity on duration t _f of the magnetizing magnetic field pulse (upon its variation from 0.4 to 6–8 ns), which is typical of these films, can be explained by the presence of biaxial anisotropy in the plane of actual films.     

The magnetization curves of thin iron films

The magnetization curves of evaporated iron films 125–7870 Åthick were measured. A torsion magnetometer was used for the magnetic measurements. In the neighbourhood of 1100 Åan anomaly was found in the dependence of the work of magnetization and a quantity which replaces remanence on the thickness of the film. Decreased density of the film in comparison with the density of the compact metal was found by weighing.     

Effect of dispersion of orthorhombic anisotropy fields on the ferromagnetic resonance linewidth in iron garnet films

The effect of the dispersion of anisotropy fields on the width of the ferromagnetic resonance line is calculated in films with orthorhombic anisotropy. The results of the calculation, based on a model of linear variation of the anisotropy fields with thickness and on the assumption of additivity of the different contributions to the resulting linewidth, are in good agreement with experimental results. Zh. Tekh. Fiz. 67, 131–134 (August 1997)     

The 50 nm-thick yttrium iron garnet films with perpendicular magnetic anisotropy

Yttrium iron garnet (YIG) films possessing both perpendicular magnetic anisotropy (PMA) and low damping would serve as ideal candidates for high-speed energy-efficient spintronic and magnonic devices. However, it is still challenging to achieve PMA in YIG films thicker than 20 nm, which is a major bottleneck for their development. In this work, we demonstrate that this problem can be solved by using substrates with moderate lattice mismatch with YIG so as to suppress the excessive strain-induced stress release as increasing the YIG thickness. After carefully optimizing the growth and annealing conditions, we have achieved out-of-plane spontaneous magnetization in YIG films grown on sGGG substrates, even when they are as thick as 50 nm. Furthermore, ferromagnetic resonance and spin pumping induced inverse spin Hall effect measurements further verify the good spin transparency at the surface of our YIG films.     

Influence of substitutions on the magnetic anisotropy of Gd-containing magnetooptic iron garnet films

The properties of magnetooptical films of the system (Bi,Gd,Ln)₃(Fe,M)₅O₁₂, where Ln = Lu or La and M = Ga or Al, grown by liquid-phase epitaxy on Nd₃Ga₃O₁₂ substrates oriented along (100), along (110), and close to (111), are investigated by x-ray and ferromagnetic resonance methods. Zh. Tekh. Fiz. 68, 113–116 (May 1998)     

Asymmetric domain nucleation and unusual magnetization reversal in ultrathin Co films with perpendicular anisotropy

We report unexpected phenomena during magnetization reversal in ultrathin Co films and Co/Pt multilayers with perpendicular anisotropy. Using magneto-optical Kerr microscopy and magnetic force microscopy we have observed asymmetrical nucleation centers where the reversal begins for one direction of the field only and is characterized by an acute asymmetry of domain-wall mobility. We have also observed magnetic domains with a continuously varying average magnetization, which can be explained in terms of the coexistence of three magnetic phases: up, down, and striped.     

Effect of the magnetic anisotropy energy distribution of MnSb clusters on spontaneous magnetization reversal of GaMnSb thin films

Temperature m(T) and time m(t) dependences of the magnetic moment of GaMnSb thin films with MnSb clusters have been measured. The m(t) dependences are straightened in semilogarithmic coordinates m(lnt). The temperature dependences of magnetic viscosity S(T) corresponding to the slope of straight lines m(lnt) have been studied. It have been demonstrated that the behavior of dependences S(T) is governed by the lognormal distribution of the magnetic anisotropy energy of MnSb clusters. It have been found that the behavior of dependences m(T) measured after the films were cooled in zero magnetic field and in magnetic field H = 10 kOe is also governed by the lognormal distribution of the magnetic anisotropy energy of MnSb clusters.     

Magneto-optic study of the behavior of magnetic domains walls in ferrimagnetic garnet films placed over samples with in-plane magnetization

Magneto-optic (MO) imaging is based on Faraday rotation of a linearly polarized incident light beam illuminating a sensitive MO layer placed in close contact to the sample. For in-plane magnetized layers of Lu_3−xBi_x Fe_5−yGa_yO₁₂ ferrimagnetic garnet films, zig-zag domain formation occurs whenever the sample stray parallel field component changes sign. In this work we study the behavior of zig-zag domain walls that appear when the garnet is placed over samples with in-plane magnetization like audio tapes recorded with different signals. We describe the zig-zag walls considering the anisotropy, exchange and magnetostatic energies in the Neel tails and the contribution of an applied magnetic field. Using different recorded signals we have been able to control the gradient of stray parallel field component on the garnet, changing the distance between domains and the size of zig-zag walls. We could even avoid the appearance of these zig-zag domain walls and obtain closed domains structures. We also study the behavior of the domain walls when an external magnetic field is applied parallel to the sample.     

Growth-induced magnetic anisotropy behavior in thin garnet films fabricated by pulsed laser deposition

The effect of target rotation rate on the magneto-optical properties and induced magnetic anisotropy of pulse laser deposition grown Bi:YIG garnets has been investigated. The rotation rate dependence of magnetic properties of thin films has been studied using magneto-optical Faraday rotation combined with magneto-optical Kerr measurement setup. Our results show that decreasing the target rotation rate can also increase the polar coercive field and hence magnetic anisotropy. Also the spectral answer of samples show the capability of use of them in one off optical ranges such as visible, near infrared and far infrared regions.     

On the local magnetization reversal in front of a domain wall moving in a garnet ferrite film with orthorhombic magnetic anisotropy

The experimentally observed shapes of dynamic domains in garnet ferrite single-crystal films with (110) and (210) orientations are explained in terms of in-plane magnetic anisotropy of these films.     

Magnetic anisotropy of europium in iron garnet

Magnetization measurements have been made of single crystals of europium iron garnet (EuIG), Ga-doped EuIG and Al-doped EuIG. Cubic anisotropy constants K₁ and K₂ have been evaluated from the magnetization curves. Temperature dependence and concentration dependence of the anisotropy are compared with the theory by Foglio and van Vleck.     

Probing the magnetization switching with in-plane magnetic anisotropy through field-modified magnetoresistance measurement

Effective probing current-induced magnetization switching is highly required in the study of emerging spin-orbit torque(SOT)effect.However,the measurement of in-plane magnetization switching typically relies on the giant/tunneling magnetoresistance measurement in a spin valve structure calling for complicated fabrication process,or the non-electric approach of Kerr imaging technique.Here,we present a reliable and convenient method to electrically probe the SOT-induced in-plane magnetization switching in a simple Hall bar device through analyzing the MR signal modified by a magnetic field.In this case,the symmetry of MR is broken,resulting in a resistance difference for opposite magnetization orientations.Moreover,the feasibility of our method is widely evidenced in heavy metal/ferromagnet(Pt/Ni₂₀Fe₈₀ and W/Co₂₀Fe₆₀B₂₀)and the topological insulator/ferromagnet(Bi₂Se₃/Ni₂₀Fe₈₀).Our work simplifies the characterization process of the in-plane magnetization switching,which can promote the development of SOT-based devices.     

On one mechanism of magnetization reversal in crystals with combined anisotropy

The effect of a magnetic field on the stability of null domain walls is considered in terms of a variational model. The walls are localized near defects in a (001)-oriented plate. The critical fields at which the inhomogeneities exist are found, and their role in magnetization processes taking place in the crystals under study is considered.     

Effect of the surface anisotropy and the shape on the magnetization behavior in an egg-shaped nanoparticle

Using the classical Heisenberg model and Monte Carlo simulation, we compute the magnetization behavior of a ferromagnetic nanoparticle with an egg-shape in an external magnetic field along the symmetry axis. The particle is in a single-domain state with a surface anisotropy axis perpendicular to the surface of the particle. At low temperature, it is found that exchange bias appears in the hysteresis loop, which does not exist in the spherical and ellipsoidal nanoparticles. The bias field produced by the frozen spins on the surface of the egg-shaped nanoparticle may be the reason to produce the phenomenon of the exchange bias.     

Kinetics of magnetization reversal in a heterophase nanomagnet with spatially modulated anisotropy

Magnetization reversal modes in a thin-film NiFeCuMo ferromagnet (FM) with periodically varying in-plane anisotropy are studied by the magneto-optical indicator film (MOIF) technique. The uni-directional anisotropy in FM regions exchange-coupled to a FeMn antiferromagnet (AFM) film in the form of square mesh stripes is alternated by the uniaxial anisotropy in the FM regions inside this mesh. It is shown that the boundaries formed along the edges of these stripes, which separate FM regions with different anisotropy, crucially influence the kinetics of domain-structure transformation in both types of FM regions. It is established that the lateral exchange anisotropy in the ferromagnet, which is determined by the stabilization of the spin distribution in the FM layer along the FM-(FM/AFM) interface, leads to the asymmetry of the magnetization reversal in FM regions bordered with an FM/AFM structure. Anisotropy of the mobility of 180-degree “charged” and “uncharged” domain walls situated, respectively, perpendicular and parallel to the unidirectional anisotropy axis is revealed. The difference observed between the mobilities of charged and uncharged domain walls is attributed to the difference in the spin distribution in these walls with respect to the unidirectional anisotropy axis and is a key factor for the difference between the magnetization reversal kinetics in horizontal and vertical exchange-biased FM stripes. Drastic differences are revealed in the asymmetry of magnetization reversal processes in mutually perpendicular narrow stripes of FM/AFM structures. Possible mechanisms of magnetization reversal in low-dimensional FM-(FM/AFM) heterostructures are discussed with regard to the effect of domain walls localized on the edges of AFM layers.