Ferromagnetic resonance in a system of magnetic films with different Curie temperatures

The peculiarities of absorption of rf electromagnetic radiation (ferromagnetic resonance) in multilayer NiFe/Ni_0.65Cu_0.35(d)/CoFe structures in a wide temperature range are analyzed. It is shown that the type of interaction of the NiFe and CoFe ferromagnetic films via a “weak” ferromagnetic Ni_0.65Cu_0.35 interlayer changes from antiferromagnetic to ferromagnetic upon cooling and a decrease in interlayer thickness d. The detected temperature dependence of the interlayer interaction indicates the possibility of observation of a strong magnetocaloric effect in the structures under investigation.     

Ferromagnetic resonance in metal films with angular dispersion of magnetic anisotropy

The specific features of the ferromagnetic resonance spectra of metal magnetic films due to the cubic crystalline anisotropy and induced uniaxial magnetic anisotropy have been studied using the statistical model of noninteracting blocks. It has been demonstrated that the inclusion of the angular dispersion of the fields of these magnetic anisotropies leads to a shift, asymmetry, and broadening of the integral resonance curve and to characteristic angular dependences of the resonance field and the resonance line width.     

Ferromagnetic resonance and magnetic crystallographic anisotropy of monocrystalline lithium ferrite films

The crystallographic anisotropy constant K₁ of monociystalline lithium ferrite films was measured by the methods of ferromagnetic resonance and rotational moments. The presence of uniaxial anisotropy in the plane of a film with the constant K_u 10₃ erg · cm^–3 is established experimentally. The nature of the uniaxial anisotropy is explained by the anisotropy of the stresses in the plane of the film, a formula is obtained to compute the angle of deflection of the easy magnetization axis from the crystallographic direction. An estimate is made of the difference in the stresses along the axes (_x–_z) 10¹⁰ dyne · cm^–2.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 16, No. 9, pp. 86–89, September, 1973.     

Ferromagnetic resonance in arrays of highly anisotropic nanoparticles

We present in this study computational simulations of the ferromagnetic resonance response of magnetic nanoparticles with a uniaxial anisotropy considerably larger than the microwave excitation frequency (in field units). The particles are assumed to be randomly oriented in a two dimensional lattice, and are coupled by dipolar interactions through an effective demagnetization field, which is proportional to the packing fraction. We have included in the model fluctuations in the anisotropy field (H_K) and allowed variations in the demagnetizing field. We then analyzed the line shape and line intensity as a function of both fields. We have found that when H_K is increased the line shape changes drastically, with a structure of two lines appearing at high fields. The line intensity has a maximum when H_K equals the frequency gap and decreases considerably for larger values of the anisotropy. The effects of fluctuations in H_K and variations in the packing fraction have been also studied. Comparison with experimental data shows that the overall observed behavior is dominated by the particles with lower anisotropy.     

Ferromagnetic resonance in films with a plane anisotropy of electrical resistivity

High conductivity of metallic films leads to attenuation of an ultrahigh frequency field at the depth of the skin layer and, consequently, to a nonuniform distribution of the high-frequency magnetization component over the film thickness. This feature leads to a shift in the frequency and to widening of the ferromagnetic resonance line in a metallic film. In the present work, we study the effect of the plane anisotropy of electrical resistivity on the resonance behavior of polycrystalline magnetic films (Ni, Co, permalloy). Appearance of this anisotropy is related to the presence in the film of extended structural defects such as microgaps oriented along the chosen direction of the substrate texture (Lavsan, mica). In the geometry of the perpendicular magnetization and the normal incident angle of the ultrahigh frequency wave with respect to the film there are two resonance frequencies corresponding to the two orthogonal polarizations of the high-frequency field.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 10–13, June, 1985.     

Ferromagnetic resonance in thin cobalt films

The paper gives the results of measuring ferromagnetic resonance on thin cobalt films, vacuum deposited on unheated glass slides. The values of the (g-factor, the width of the curve, the effective stress and uniaxial induced anisotropy were determined as a function of the thickness of the film from measurements of the ferromagnetic absorption in a magnetic field normal and parallel to the surface of the film. Measurements were carried out on a frequency of 9200 MHz and on film thicknesses of 180 to 1800 Å. A qualitative explanation of the observed dependences is given.

---

, . , , g-, , , . 9200 MHz 180–1800 Å. .

---

---

The author thanks V. Kamberský and Z. Málek, C. Sc., for providing some of the cobalt films and for help in depositing and measuring the thicknesses, S. Kadeková and M. Polcarová for valuable advice in determining the structure of the films, J. Míová for carefully plotting the results of measurements and Z. Málek and O. tirand for carefully reading the paper and for valuable discussions.     

Ferromagnetic resonance in interacting magnetic microstrips

The results of the micromagnetic simulation of forced oscillations of the magnetization in a system of two interacting microstrips located at an angle to each other have been presented. The ferromagnetic resonance spectra and the mode composition of resonant oscillations of the system have been investigated under the conditions of magnetostatic and exchange interactions between the microstrips. It has been shown that the magnetostatic interaction leads to the possibility of the excitation of in-phase and out-of-phase coupled oscillations of the magnetization of the microstrips. In the systems of exchange-coupled microstrips, there are intense resonances due to oscillations of the domain walls. The transformation of the ferromagnetic resonance spectrum and the change in the mode composition of resonant oscillations in different equilibrium configurations of the magnetization of the system have been discussed, as well as the conditions for the excitation of oscillations of different types depending on the direction of the microwave magnetic field.     

Characteristic features of ferromagnetic resonance in iron-garnet films with orthorhombic magnetic anisotropy

The characteristic features of ferromagnetic resonance (FMR) were studied in bismuth-containing single-crystal iron-garnet films (BSIGFs) with no rapidly relaxing ions and relatively weak orthorhombic magnetic anisotropy (ORMA). The films were grown on (110) and (210) substrates by liquid-phase epitaxy from a supercooled flux solution. Attention is focused mainly on the unidirectional magnetic anisotropy in the film plane and on the effect of the film/substrate transitional surface layer on the FMR spectrum. Fiz. Tverd. Tela (St. Petersburg) 41, 1254–1258 (July 1999)     

Ferromagnetic resonance in polycrystalline ferrites with high magnetic anisotropy

The ferromagnetic resonance absorption line is computed in polycrystalline ferrites in the independent grain approximation taking account of the magnetic crystallographic and magnetostriction anisotropies. The results obtained show that the influence of elastic stresses on the shape of the absorption line is analogous to the effect of the magnetic crystallographic anisotropy.Translated from Izvestiya VUZ. Fizika, No. 1, pp. 9–16, January, 1972.     

Ferromagnetic resonance studies in compositionally modulated cobalt-niobium films

We have prepared multilayered compositionally modulated films by alternately depositing Co and Nb layers of 50 and 24 Å nominal thickness, respectively. Two e-beam evaporation systems in ultra high vacuum were used. Magnetization and B-H loop measurements were done at 293 K. Ferromagnetic resonance was observed at 9.79 GHz using cavity techniques and as a function of frequency in the range 4–14 GHz using a planar microwave structure. The magnetization 4πM=13 kG is found to be lower than the Co bulk value. The observed frequency dependence of the linewidth in the parallel orientation can be interpreted. Possible explanations for the reduction of 4πM are discussed.     

Ferromagnetic resonance studies in granular CoCu codeposited films

Experimental ferromagnetic resonance (FMR) data are presented for CoCu granular films obtained by electron beam codeposition. Co_xCu_100−x films were prepared for x=10 and 30 and were subsequently submitted to a thermal treatment. For the 10% Co samples one found three main resonance modes, one of them constituting of non-interacting Co particles. External field angular variation and temperature-dependent FMR experiments were proceeded and straight calculations of the involved resonance intensities as well. A strict correlation of the presented FMR data with the previous X-Ray diffraction, magnetization, and particle size investigations was possible. The link between structural changes and magnetic properties of the samples could be verified. For the 30% Co samples a broad resonance line for the in-plane configuration was found, which is characteristic for polycrystalline systems. In the perpendicular configuration a spin wave spectra were present on all samples and one could identify some of the modes as surface modes. These samples with 30% Co become more heterogeneous with increasing thermal treatment.