Linewidth of ferromagnetic resonance in holmium yttrium garnet ferrites

The specific features experimentally observed in the behavior of the linewidth of ferromagnetic resonance in holmium yttrium garnet ferrites were investigated as a function of the orientation of the external magnetic field at low temperatures. The analysis was performed using the model spectrum of holmium ions, according to which the ground state of these ions is represented by two closely spaced levels (quasi-doublet) that are sufficiently far removed from the other levels. A comparison of the theoretical results with the experimental data was carried out.     

Equation of the ferromagnetic resonance line in polycrystalline ferrites

Ferromagnetic resonance in polycrystalline ferrites is considered in the framework of the independent-grain model. It is shown that the ferromagnetic resonance absorption line can be obtained analytically from its moments. When a limited number of moments of the line are known explicitly, the method of Pearson curves is used to obtain the equation of the line. The obtained expression is analyzed and the resonance field and absorption line width deduced from the equation are compared with results obtained earlier.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 19–23, March, 1981.     

Comparison between disaccommodation and ferromagnetic resonance measurements in polycrystalline nickel ferrites

FerroMagnetic Resonance (FMR) measurements of polycrystalline nickel ferrites at 11 GHz from 77 to 400 K have been carried out. The different contributions to the FMR linewidth have been studied by a computational technique based on the parameters previously obtained for single-crystal nickel ferrite. A new qualitative comparison between the FMR and disac-commodation measurements by means of the induced anisotropy formalism is presented.     

Effect of pores and nonmagnetic inclusions on ferromagnetic resonance in polycrystalline ferrites

In this paper an account is given of the experimental results concerning the effect of pores and nonmagnetic inclusions on the ferromagnetic resonance line parameters in polycrystalline ferrites. Calculations of linewidth, resonance field, and first moment are compared with experiment in a wide range of porosity. The effect of porosity on the frequency dependence of the linewidth is discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 112–115, February, 1982.     

A contribution to the study of ferromagnetic resonance in manganese zinc ferrites

A study is made of the temperature dependence of ferromagnetic resonance in the 9300 Mc band on three samples of manganese zinc ferrite. The results are discussed from the point of view of the Tsuya model for the production of an additional internal field during ferromagnetic resonance.     

On the problem of the internal effective field for ferromagnetic resonance of polycrystalline ferrites

A study was made of the ferromagnetic resonance of MnZn ferrite in the temperature region –124 °to +182 °Cin the 3 cmband. The additional internal effective field and its temperature dependence was determined. A comparison with the results of measurements of the initial permeability carried out at the same time pointed to the close relationship between magnetocrystalline anisotropy and the additional field or apparent value of the Landé factor g.     

Influence of inhomogeneous exchange interaction on the moments of the ferromagnetic resonance lines in polycrystalline ferrites

From the viewpoint of the spin-wave approach to the theory of ferromagnetic resonance, the first four moments of the absorption line are calculated in this paper. It is shown that in addition to the magnetic dipole-dipole interaction, the inhomogeneous exchange interaction which has been neglected in previous papers exerts substantial influence on the asymmetry and peakedness of the ferromagnetic resonance line.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 75–78, July, 1979.     

Independent cluster model of ferromagnetic resonance linewidth broadening in Mn x Fe3−x O4 ferrites

The previously developed simple theory of ferromagnetic resonance linewidth broadening due to the thermal processing of the material, that was observed e.g. in Mn-ferrites, is reconsidered using the recently published independent-cluster model of two-phase systems. The composition, temperature, and angular dependences of the linewidth are explained, in good qualitative agreement with experiment. An estimate of cluster size necessary for the explanation of the observed effect is given. The theory seems to confirm the assumed connection between clustering and linewidth broadening for slowly cooled samples.The author would like to express his thanks to Dr. S. Krupika, the discussions with whom were of great help during this work.     

Phonon propagation in ferromagnetic resonance

In addition to the known electromagnetic transmission mode in thick ferromagnetic foils, a new transmission resonance effect is described which, following the work of Blackstead and collaborators, is conjectured to be excited through magnetoelastic coupling. It appears that this new transmission signal is propagated through the sample via phonon-magnon modes.     

Magneto-optical resonance in ferromagnetic gadolinium

The optical constants n and k of ferromagnetic and paramagnetic gadolinium have been measured, at various temperatures, from polarimetric measurements, in the low energy range 0.5 to 1.5 eV. For the ferromagnetic state, evidence of extra-optical conductivity is found near 0.69 eV and attributed to magnetic ordering. It confirms Miwa and Mackintosh predictions, assuming that new energy gaps are introduced in the conduction band through the s-f exchange interaction. From the experimental determination of the energy gap resulting from a splitting of the conduction band between spin up and spin down bands, we have deduced the effective s-f exchange energy J(q) = 1.58 × 10^-13 erg.     

Ferromagnetic resonance line dispersion in polycrystalline ferrites

Results of a theoretical and experimental investigation of the influence of pores and nonmagnetic inclusions on the ferromagnetic resonance line dispersion in polycrystalline ferrites are elucidated in this paper. The absorption line dispersion is computed with the deflection of the local magnetization vector from the magnetizing field direction taken into account, where the dispersion is described by linear terms in the generation and annihilation operators in the Hamiltonian of the interacting spin wave system. The theory and experiment are compared in a broad range of variation of the porosity in different ferrites. The field of anisotropy of the ferrites investigated is calculated from the second moment of the absorption line.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 37–41, November. 1981.     

Dissipative boundary conditions for ferromagnetic resonance equations

Surface scattering of electrons and magnons results in nonuniform dissipation of the energy of ferromagnetic resonance (FMR) modes. This surface damping may be included in proper boundary conditions for the magnetic differential equations of motion, which are derived phenomenologically in the same way as the usual spin-pinning conditions. An analysis of the local energy balance in non-uniform modes leads to the concept of spin-wave energy flow; the dissipative boundary conditions describe the flow of the coherent mode energy into the surface. The magnitude of the surface damping parameters is only crudely estimated. Numerical calculations of the FMR linewidth and the shapes of standing-spinwave spectra indicate that experimentally significant effects may appear with damping parameters near to the estimated upper limits.     

Spin wave stiffness parameters in lithium-zinc ferrites

The spin wave exchange stiffness has been calculated for a series of zinc substituted lithium ferrites and compared with measured values obtained by Brillouin light scattering. The theory yields values of 2.9×10⁻⁹ to 0.9×10⁻⁹ Oe-cm², relative to the observed values of 11.6×10⁻⁹ to 0 Oe-cm², for 0 to 0.4 Zn at./ formula unit, respectively.     

铁磁和反铁磁双层膜中铁磁共振的研究

采用微磁学理论研究了铁磁/反铁磁双层膜中的铁磁共振现象.本模型将铁磁薄层抽象为一个单晶,具有立方磁晶各向异性和单轴磁晶各向异性,而反铁磁层视为厚度趋近于半无穷,且只有单轴磁晶各向异性.推导出了该系统的铁磁共振频率和频率谱宽度的解析式.数值计算表明,铁磁共振模式分两支,取决于立方磁晶各向异性.而界面的交换耦合,是磁易轴具有单向性的起因.     

On ferromagnetic resonance damping in metals

The Landau-Lifshitz damping coefficient is defined in terms of spin-orbital torque correlations in the one-electron model and estimated as a function of the orbital collision frequency. The formal results are compared with previous studies and the results of a numerical calculation for nickel are compared with known experimental data.I would like to thank Dr. L.Hodges for a copy of his thesis and Dr. A. V.Gold, Dr. J. R.Anderson, Dr. V.Dvoák, Dr. Z.Frait and Mr. M.Kolá for valuable discussions at various stages of this work.