Strongly enhanced magnetic moments of vanadium impurities in thin films of sodium and potassium

Thin quench-condensed films of Na and K are covered with 1/100 of a monolayer of V. Then the impurities are covered with several atomic layers of the host. The magnetization of the films is measured by means of the anomalous Hall effect. For V impurities on the surface of Na and K, a magnetic moment of 7 Bohr magnetons is observed. After coverage with the host, the V moment became 6.5 mu(B) for the Na host. These results contradict the favored atomic model (predicting 3/5 mu(B)) and the resonance model. A polarization of the alkali host appears to be the only resolution.     

Intrinsic distribution of magnetic anisotropy in thin films probed by patterned nanostructures

We demonstrate that the switching field distribution (SFD) in arrays of 50 nm to 5 microm Co/Pd elements, with perpendicular anisotropy, can be explained by a distribution of intrinsic anisotropy rather than any fabrication related effects. Further, simulations of coercivity and SFD versus element size allow the distribution of intrinsic anisotropy to be quantified in highly exchanged coupled thin films where the reversal mechanism is one of nucleation followed by rapid domain wall motion.     

Micromagnetic simulation of the magnetic dispersion angle and effective damping factor for the single-phase soft magnetic films

The micromagnetic structure of the single-phase soft magnetic films was simulated using the model of two-dimensional hexagonal lattices by micromagnetic method. The typical micromagnetic ripple structure of magnetic films was obtained. Thus, the magnetic dispersion angle was calculated from the static magnetic structure of the film. Furthermore, the relationship between the magnetic dispersion angles and the corresponding magnetic parameters of the film was discussed. The technique also demonstrated the microwave permeability of the films and the magnetic spectra well fitted by the permeability equation, which was deduced from the Landau–Lifshitz–Gilbert (LLG) function when the film was considered as a single domain. The fitting data of effective damping factor as a function of the magnetic dispersion angle were investigated.     

L1_0-FePt合金单层磁性薄膜的微磁学模拟

具有四方结构的L10-FePt合金因其具有高磁晶各向异性和良好的化学稳定性而成为超高密度薄膜磁记录介质的最佳选择.对实验制备得到的磁性能良好的垂直取向L10-FePt合金单层膜进行了微磁学分析.在传统微磁学模型的基础上,根据晶体的对称性,引入了四角磁晶各向异性能密度的唯象表达形式;又依据薄膜生长过程中晶格对称性的破坏,考虑了薄膜面内的应力,并引入了磁弹性能.以四角磁晶各向异性能和磁弹性能为重点,对L10-FePt合金单层膜的磁滞回线进行了详细的分析,并且用微磁学方法确定了薄膜面内应力的大小.     

Thickness transitions in thin films: The equilibrium

The thermodynamic and thickness equilibria of planar solid, liquid or gaseous thin films are described in terms of the film excess chemical potential μ_ex. A general formula is given which relates μ_ex to the short- and/or long-range surface forces associated with the two film surfaces and the dependence of the film specific surface free energy σ on the film thickness h is expressed through μ_ex. The conditions under which the thin films are in stable or metastable thermodynamic equilibrium are analyzed and it is shown that the metastable thin films are subject to thickness transitions involving abrupt changes of h. The thin film thickness equilibrium, i.e. the coexistence between two films of different thickness, is also considered and the film equilibrium chemical potential characterizing this equilibrium is determined by means of μ_ex and σ.     

A quark shell model calculation of nuclear magnetic moments

The “Schmidt lines” for nuclear magnetic moments are calculated in a quark shell model. In the pairing scheme proposed by Petry et al., the single-nucleon magnetic moment is simply related to the single quark value. The isoscalar part is essentially the same as that of the conventional Schmidt moment while the isovector part increases too rapidly as the angular momentum increases. Possibilities of improving the model are briefly discussed.     

Depth-resolved magnetization distribution in ultra thin films by soft X-ray resonant magnetic reflectivity

The analysis of complex magnetic profiles throughout an ultrathin magnetic films by soft X-ray resonant magnetic reflectivity is discussed. Subnanometer resolution can be achieved allowing the separation of interface and inner layer magnetic contributions as well as the determination of antiferromagnetic and non-collinear spin structures. Reflectivity measurements are carried out up to large scattering angles allowing the determination of the depth-resolved profiles of the out-of-plane magnetic component.     

Stability of nonthermodynamic equilibrium cation distribution frozen during pulsed laser deposition of Co-ferrite thin films

Co-ferrite thin films were prepared by pulsed laser deposition technique at room temperature, and magnetization was studied as a function of annealing temperature (T _A ) and annealing time. One set of films was quenched immediately after annealing while the other set was furnace cooled. Spontaneous magnetization value, 4π M _S , of the quenched films was observed to be higher than the furnace cooled films in all the cases. Magnetization increases monotonically up to T _A =650°C and then became nearly constant with the increase in T _A . Magnetization values even higher than the Co-ferrite bulk value of 5300 G was observed in the quenched films annealed at and above 650°C. In the case of furnace cooled films, magnetization decreased with the increase in annealing time, while it remained nearly constant in quenched films. Coercivity values of the quenched films were always found to be lower than those of the furnace cooled films. The observed magnetic properties in the films were attributed to the cation distribution and the grain sizes.     

Computer calculation of fanning spin structure in magnetic thin films and determination of exchange stiffness constant

Magnetization curves and critical switching curves were calculated numerically for fanning flux reversal of magnetic thin films and compared with the experiment in which the fanning spin structure was realized by a twisting field produced by the in-plane current followed by an external field in the reverse direction. From the best fit of the experimental and calculated curves, values of the exchange stiffness constant,A, were determined for Ni-Fe and Ni-Fe-Co films.The authors would like to thank Dr. Nobuo Hayashi of the Department of Physics, Faculty of Science, University of Tokyo, for useful discussions on calculations.     

Microwave magnetic properties of soft magnetic thin films

We review our works that focus on the microwave magnetic properties of metallic,ferrite and granular thin films.Soft magnetic material with large permeability and low energy loss in the GHz range is a challenge for the inforcom technologies.GHz magnetic properties of the soft magnetic thin films with in-plane anisotropy were investigated.It is found that several hundreds of permeability at the GHz frequency was achieved for Co100-xZrx and Co90Nb10 metallic thin films because of their high saturation magneti...     

Critical behavior of magnetic thin films

We study the critical behavior of magnetic thin films as a function of the film thickness. We use the ferromagnetic Ising model with the high-resolution multiple histogram Monte Carlo (MC) simulation. We show that though the 2D behavior remains dominant at small thicknesses, there is a systematic continuous deviation of the critical exponents from their 2D values. We explain these deviations using the concept of “effective” exponents suggested by Capehart and Fisher in a finite size analysis. The shift of the critical temperature with the film thickness obtained here by MC simulation is in an excellent agreement with their prediction.     

Rotation of the magnetic moment of thin films

The remagnetization time of thin magnetic fields for remagnetization along the axis of hard magnetization has been calculated on a computer. It is found that the magnetic moment may flip from a position along the axis of easy magnetization to the opposite direction under the influence of a pulsed magnetic field along the axis of hard magnetization.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vo. 12, No. 3, pp. 104–107, March, 1969.The author thanks G. M. Rogichev for discussion of and assistance in this study.     

Element-selective mapping of magnetic moments in ultrathin magnetic films using a photoemission microscope

We combine X-ray magnetic circular dichroism (XMCD) and photoelectron emission microscopy to obtain locally resolved magnetic information on a microscopic scale. Scanning the photon energy across elemental absorption edges and recording microscopic images of the local secondary electron intensity for both photon helicities at each photon energy step allows to analyze local XMCD spectra at any position of the imaged area of the sample. With the help of magnetic sum-rules local quantitative information about magnetic moments can be extracted from such microspectroscopic measurements. The full power of XMCD as a spectroscopic tool is so maintained, while microscopic spatial resolution is added.     

Anisotropic magnetocaloric effect in thin magnetic films

We consider the magnetocaloric effect in thin magnetic films. The experimental method is based on heat transfer in a layered structure containing a magnetic film and a film of material with a metal-dielectric phase transition. The anisotropy of the magnetocaloric effect is studied.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 40–43, November, 1989.The authors thank G. A. Petrakovskii and V. G. Pyn'ko for useful discussions.     

Self-focusing magnetostatic beams in thin magnetic films

The possibility of generation of stable self-focusing beams in in-plane magnetized thin magnetic films is considered, and theoretical conditions for the existence of such localized solutions are discussed. It is shown that for the definite direction between static magnetizing field and preferential direction of radiation from a microwave antenna, the problem reduces to the one-dimensional nonlinear Schrödinger equation. For such angles it is possible to generate stable self-focusing beams. Particular values of beam width and propagation angles versus magnitude of magnetizing field are calculated in order to suggest a realistic experimental setup for the observing the discovered effect.Received: 3 July 2004, Published online: 12 October 2004PACS: 85.70.Ge Ferrite and garnet devices - 75.30.Ds Spin waves - 76.50. + g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance