Properties Of Ferromagnetic Thin Films Research Articles

Microstructure and Magnetic Properties of the CoTiO2 Thin Films

Co (t nm)/TiO2(200 nm) films were prepared by DC facing-target magnetron reactive sputtering system onto glass substrates at room temperature. The influence of the Co distribution on microstructure and magnetic properties of films was investigated in detail. The results indicate that CoTiO2thin films with t= 2 nm island-type deposited showed a homogeneous structure, and pure ferromagnetic properties of thin films are only attributed to the CoTiO2phases. On the other hand, in case of thin films above t= 2nm, the overall ferromagnetic properties depended on both CoTiO2and CoTi phases.

P-G2-4 微細加工した強磁性体の磁気特性と電気伝導特性(P-G2 マイクロナノ材料・構造,ポスターセッション論文)

This paper gives how to design the magnetic and electronic properties of ferromagnetic thin film with micro structures. In this research, a hard ferromagnetic thin film with anisotropic hole array made by electron-beam lithography is used. It is found that the ferromagnetics with anisotropic micro structures has an anisotropic coercivity microscopically, and it has some steps in magnetization curve macroscopically. The anisotropic structures also make a difference in magneto-resistance properties.

Tuning of magnetization dynamics by ultrathin antiferromagnetic layers

The controlled adjustment of static and dynamic magnetic properties of ferromagnetic thin film by the use of ultrathin antiferromagnetic layers is demonstrated. Induced uniaxial anisotropy and thus precessional frequency is increased over more than one order of magnitude. Concurrently, the effective damping parameter is varied by which a significant decrease in magnetic settling time is achieved. Simple relations based on the interfacial antiferromagnetic layer contribution are derived. The use of ultrathin antiferromagnetic layers, below the thickness range for the onset of exchange bias, allows for tuning of magnetic properties beyond the established manipulation of the intrinsic ferromagnetic layer properties.

In situmanipulation of magnetic anisotropy in magnetite thin films

We show that the ferromagnetic anisotropy of a thin crystalline ${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}$ film can be manipulated in situ via the application of tunable stress. The stress is exerted by a piezoelectric actuator, onto which the ${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}$ film is cemented. The strain in the sample is quantified as a function of the voltage applied to the actuator using high-resolution x-ray diffraction, and the corresponding evolution of the magnetic anisotropy is determined by ferromagnetic resonance spectroscopy. By this means, we are able to directly correlate structural and magnetic properties. The experimental results demonstrate that a piezoelectric actuator allows to substantially modify the magnetic anisotropy of a crystalline ferromagnetic thin film, enabling a voltage control of magnetization orientation. The possibility to orient the main elongation axis of the actuator along any given direction in the film plane opens a pathway for the investigation of the magnetoelastic properties of ferromagnetic thin films under tunable stress, shear, or combinations of both stress and shear.

Magnetic properties of a thin quantum spin [formula omitted] Heisenberg film

The magnetic properties of thin ferromagnetic films are investigated within quantum spin 1 2 Heisenberg model, using the correlated effective-field theory (EFT). We calculate some magnetic properties of the film such as the layer magnetizations, their averages, profiles and longitudinal susceptibility. The film longitudinal susceptibility still diverges at the film critical temperature, while the magnetization approaches are going to zero.

Diluted Magnetic Semiconducting Ti1 − xCox O 2 Thin Films Grown onto SiO2 ( 200 nm ) / Si Substrates by Liquid-Delivery MOCVD

Anatase thin films onto substrates at 400°C using liquid-delivery metallorganic chemical vapor deposition (MOCVD) were successfully prepared and the ferromagnetic properties investigated through microstructural analysis by transmission electron microscopy and high-resolution scanning Auger microscopy as a function of Co-doping concentration. Ferromagnetic behaviors of polycrystalline films were observed at room temperature and the magnetic and structural properties depend critically on the Co distribution, which varies widely with Co-doping concentration. Annealed thin films with showed a homogeneous structure without any clusters, and pure ferromagnetic properties of thin films are attributed only to the phases. In the case of thin films above Co-rich clusters are formed in homogeneous phases. The solid solubility of Co was approximately 5 atom % in polycrystalline thin films. clusters with a c axis preferred orientation decrease the value of (coercive field) and increase the saturation magnetic field. The polycrystalline anatase thin films prepared by liquid-delivery MOCVD have an advantage for high-density device application in ferromagnetic semiconductor fields. © 2004 The Electrochemical Society. All rights reserved.

Microstructure and Magnetic Properties of Ti1-xCoxO2 Diluted Magnetic Semiconductor Thin Films with Various Co Concentrations by Metal Organic Chemical Vapor Deposition

Polycrystalline <TEX>$Ti_{l-x}$</TEX> <TEX>$Co_{x}$</TEX> <TEX>$O_2$</TEX>thin films on <TEX>$SiO_2$</TEX> (200 nm)/Si (100) substrates were prepared using liquid-delivery metalorganic chemical vapor deposition. Microstructures and ferromagnetic properties were investigated as a function of doped Co concentration. Ferromagnetic behaviors of polycrystalline films were observed at room temperature, and the magnetic and structural properties strongly depended on the Co distribution, which varied widely with doped Co concentration. The annealed <TEX>$Ti_{l-x}$</TEX> <TEX>$Co_{x}$</TEX> <TEX>$O_2$</TEX>thin films with <TEX>$x\leq$</TEX>0.05 showed a homogeneous structure without any clusters, and pure ferromagnetic properties of thin films are only attributed to the X<TEX>$l-x_{l-x}$</TEX> <TEX>$Co_{x}$</TEX>X<TEX>$O_2$</TEX>phases. On the other hand, in case of thin films above x = 0.05, Co-rich clusters formed in a homogeneous <TEX>$Ti_{l-x}$</TEX> <TEX>$Co_{x}$</TEX> <TEX>$O_2$</TEX>phase, and the overall ferromagnetic (FM) properties depended on both FMTCO and FMCo. Co-rich clusters with about 10-150 nm size decreased the value of Mr (the remanent magnetization) and increased the saturation magnetic field.

Broadband ferromagnetic resonance spectrometer

The continuous wave ferromagnetic resonance (FMR) spectrometer operating in multioctave (0.05–40 GHz) frequency range has been built to investigate the magnetic properties of thin ferromagnetic films in the temperature range of 4–420 K. The spectrometer has two probeheads: one is the X-band microwave reflection cavity used to perform express room temperature measurements and the other is an in-cryostat microstrip line probe to carry out FMR experiments covering the entire frequency range offered by the microwave source. Very uniform and stable magnetic field up to 2.4 T, temperature 4 K–420 K, and continuous frequency scan performed by an HP8722D vector network analyzer provide various modes of operation. Both probe heads are equipped with two-circle high precision goniometers to ensure accurate characterization of magnetic anisotropy and magnetostatic waves spectra recording. Use of the phase sensitive detection, utilized by magnetic field modulation at audio frequency and computer triggering of the network analyzer, enables broadband spectrometer sensitivity to be as high as 1.3×1011 spins/Oe.

Dynamic exchange coupling and Gilbert damping in magnetic multilayers (invited)

We theoretically study dynamic properties of thin ferromagnetic films in contact with normal metals. Moving magnetizations cause a flow of spins into adjacent conductors, which relax by spin flip, scatter back into the ferromagnet, or are absorbed by another ferromagnet. Relaxation of spins outside the moving magnetization enhances the overall damping of the magnetization dynamics in accordance with the Gilbert phenomenology. Transfer of spins between different ferromagnets by these nonequilibrium spin currents leads to a long-ranged dynamic exchange interaction and collective excitation modes. Our predictions agree well with recent ferromagnetic-resonance experiments on ultrathin magnetic films.

Many-body Green's function theory for thin ferromagnetic anisotropic Heisenberg films: treatment of the exchange anisotropy

The many-body Green's function theory developed in our previous work for treating the reorientation of the magnetization of thin ferromagnetic films is extended to include the exchange anisotropy. This leads to additional momentum dependencies which require some non-trivial changes in the formalism. The theory is developed for arbitrary spin values S and for multilayers. The effects of the exchange anisotropy and the single-ion anisotropy, which was treated in our earlier work, on the magnetic properties of thin ferromagnetic films are compared.

Effects of Co-doping level on the microstructural and ferromagnetic properties of liquid-delivery metalorganic-chemical-vapor-deposited Ti1−xCoxO2 thin films

Polycrystalline Ti1−xCoxO2 thin films on SiO2 (200 nm)/Si (100) substrates were prepared using liquid-delivery metalorganic chemical vapor deposition, and the microstructure and ferromagnetic properties were investigated as a function of doped Co concentration. Ferromagnetic behaviors of polycrystalline films were observed at room temperature, and the magnetic and structural properties strongly depended on the Co distribution, which varied widely with doped Co concentration. The annealed Ti1−xCoxO2 thin films with x⩽0.05 showed a homogeneous structure without any clusters, and pure ferromagnetic properties of thin films are only attributed to the Ti1−xCoxO2 (TCO) phases. On the other hand, in case of thin films above x=0.05, Co1−xTix clusters having a soft magnetic (SM) property formed in a homogeneous Ti1−xCoxO2 phase, and the overall ferromagnetic (FM) properties depended on both FMTCO and SMCo–Ti. Co1−xTix clusters with about 150 nm size decreased the value of Hc (coercive field) and increased the saturation magnetic field.

Fluctuation–dissipation considerations for phenomenological damping models for ferromagnetic thin films

Dissipation properties of ferromagnetic thin films are traditionally characterized by phenomenological damping models related to ferromagnetic resonance (FMR) linewidths. They may also be analyzed in terms of thermal magnetization fluctuations, the connection being made through the fluctuation–dissipation theorem. This article describes how fluctuation–dissipation relations provide a means for discriminating between alternative phenomenological magnetic damping models in ways that are not obvious using traditional uniform-magnetization descriptions appropriate to FMR experiments. In particular, it is shown that recently proposed alternatives to the well-known Gilbert damping model lead to physically untenable predictions/contradictions when analyzed in this light, unlike the traditional Gilbert model itself.

Magnetic field dependence of phase transitions in ferromagnetic semiconducting thin films

A Green's function technique is used to investigate the properties of ferromagnetic thin films in an external magnetic field. The thicker films reach the saturation at much lower applied fields than the thinner films.

High frequency, small signal MH loops of ferromagnetic thin films.

A method is presented for transforming the high frequency bias susceptibility measurements of ferromagnetic thin films into the form of a MH loop with, depending upon the measurement geometry, the y-axis zero crossing giving a measure of the coercive force or anisotropy field. The loops provide a measure of the quantitative and qualitative high frequency switching properties of ferromagnetic thin films.

Static and dynamic properties of ferromagnetic thin films with stripe domain structure

We investigate the properties of ferromagnetic films deposited by magnetron sputtering, with a stripe domain structure. The domain structure is visualized by Kerr microscopy. We propose a model based on the minimization of a free energy of the stripe system, which allows us to fit the complete hysteresis curve. We can deduce the domain period and the magnetic parameters from the experimental hysteresis curve. We obtain a reasonable agreement on the stripe width with our observations, and with previous works. The dynamic response in the 10 MHz to 3 GHz range is also studied. The resonance frequencies are computed by the Smit and Beljers method. The calculated resonance frequencies are in good agreement with our observations.

Isotropic in-plane external stressing of ferromagnetic films

Magnetoelastic effects due to internal stress strongly influence the magnetic properties of thin ferromagnetic films. Here we propose a method to create a tensile stress state, isotropic along the plane of the film, which superimposes on the intrinsic stress (also normally isotropic). Thus the study of the effects of deposition or epitaxial stresses onto anisotropy properties of thin films becomes feasible. As an application, magneto-optical polar Kerr hysteresis loop measurements have been carried out on Ni films electroplated on elastic bronze substrates; the magnetoelastic anisotropy created reduces the total in-plane anisotropy field of about 20% for a radial deformation of 3/spl middot/10/sup -3/, around 100 times the saturation magnetostriction of bulk Ni.

Some Magnetic Properties of Thin Ferromagnetic Films in the Coherent Potential Approximation (S = 1)

AbstractThe coherent potential approximation method taking into account natural disorder connected with different states of spin components is applied to thin magnetic films with spin S = 1. The distribution of spontaneous magnetization as well as the temperature dependence of the critical temperature are obtained for b.c.c. (100) films. The results obtained using Tyablikov decoupling of higher order Green function are improved in relation to the Green function results obtained with the same decoupling procedure by including the line profiles of elementary excitations.

Thickness dependence of the magnetization and the Curie temperature of ferromagnetic thin films

The magnetic properties of thin ferromagnetic films are studied using a mean-field model. The thickness dependent film Curie temperature Tc(d) is calculated for different surface magnetic moments μs as well as for different lattice types and -faces. For an enhanced μs the bulk Curie temperature Tc(∞) can be reached within a few layers or may even be exceeded. The layer dependent magnetization curves mi(T) are calculated for a few systems, assuming Ising as well as Heisenberg type spins. Thermal fluctuations are partly taken into account by an improved mean field theory. The main features of our results seem to be presented in the presence of fluctuations.

Magnetic Properties of Thin Films with a Gaussian Distribution of Exchange Integrals

AbstractMagnetic properties of thin ferromagnetic films with Gaussian distribution of the exchange integrals are investigated in the framework of the Ising model. The correlation functions corresponding to Matsudaira's third approximation are taken into account. The numerical results for phase diagrams, magnetisation, and correlation functions are presented, and in the discussion a comparison with the results obtained for the Handrich‐Kaneyoshi distribution is made.

Electronic and magnetic properties of thin ferromagnetic films

We have carried out self-consistent calculations on single and few- layer films of ferromagnetically ordered iron metal with and without Pd overlayers. The calculations are based on the (relativistically extended) density functional theory of Hohenberg, Kohn and Sham [1,2] by means of which the N-electron problem of the system in question can be mapped onto a one-electron problem. The latter consists in Dirac-type one-particle equations which have to be solved self-consistently. In the present study this has been achieved by employing a relativistic version of the FLAPW method of Freeman et al. [3]. This method has proved to yield the most accurate solutions to the one-particle equations. Hence, also hyperfine fields can reliably be determined within that scheme, at least in principle. We have, in addition, calculated the magnetic anisotropy energy for a Fe(001) monolayer.