Microstructural characterization is key to determining the structure-property-processing relationships required to optimize the performance of magnetic thin films for longitudinal magnetic recording. Since the grain size of modem recording media is on the order of 10 to 20 nm, only high-resolution characterization methods such as transmission electron microscopy (TEM) can accurately describe the microstructure. Complete analysis requires a combination of conventional and high-resolution TEM imaging with analytical methods such as energy dispersivespectroscopy and energy-filtered TEM imaging. This paper provides examples from CoCr(Pt,Ta) alloys that reveal the strengths and limitations of these characterization methods as they apply to microstructural characterization of magnetic thin films.

Two different types of polycrystalline films, films with low (Fe) and films with high (Co50Fe50) saturation magnetostriction λs, were sandwiched between Cu to study the thickness dependence of λs in Cu/X/Cu systems. We utilised a new method (ROTMOKE) for a high accurate Hk determination. The values for X, were determined by analysing the change of Hk during application of compressive and tensile stress by cylindrical bending of the substrate joint with the film. For both systems, a remarkable contribution of the interface to the λs, was found. The sign of the interface contribution is opposed to the sign of bulk λs, leading to a zero transition of λs., For Fe this transition occurs at a thickness of 5 nm whereas for the CoFe film with a strong λs, value of the bulk of around 80 · 10−6 a transition was extrapolated at a thickness around 1 nm.

We have studied the magnetic and structural properties of thin electrodeposited Co and Cu layers grown directly onto (100) n-GaAs and have investigated the influence of a buffer layer. A dominant fourfold anisotropy with a uniaxial contribution is observed in 10 nm Co electrodeposited films on GaAs. An easy axis is observed in the [001] GaAs direction with two hard axes of differing coercivities parallel to the [011] and [011] directions. For thicker films the easy axes in the [001] direction becomes less pronounced and the fourfold anisotropy becomes less dominant. Co films of similar thicknesses deposited onto an electrodeposited Cu buffer layer were nearly isotropic. From X-ray diffraction 21 nm Co layers on GaAs were found to be hcp with the c-axis tending to be in the plane of the film. The anisotropy is ascribed to the Co/GaAs interface and is held responsible for the unique spin-valve properties seen recently in electrodeposited Co/Cu films.

Thin Co and Co based alloy films with the face centered cubic (FCC) structure have been epitaxially grown on single crystal Si wafers by sputter deposition. Epitaxial orientation relationships have been determined by x-ray diffraction, x-ray pole figure scans and TEM. Magnetic properties have been characterized using vibrating sampling magnetometer (VSM), torque magnetometer and BH loop tracer. Soft magnetic properties have been observed for the pure Co films.

Recently we have developed a robust GMR material system, based on an artificial antiferromagnet which is exchange-biased with Ir-Mn. By combining magnetoresistance and magnetization measurements with Transmission Electron Microscopy analyses we show that the degree of [111] texture has direct effects on the sensor properties of the GMR multilayer. The degree of texture turns out to depend not only on the buffer layer, but also on the thickness of the Ir-Mn layer. The strongest texture is found for Ir-Mn layer thicknesses of around 4 nm. For this thickness the largest exchange-biasing field and GMR ratio are also obtained (after cooling in a magnetic field), but the blocking temperature is significantly reduced. If attention is paid to the material structure by choosing the right materials, layer thicknesses and stack order, a robust GMR multilayer system can be made that can withstand high temperatures (> 200°C) and strong magnetic fields (> 200 kA/m), as has been demonstrated experimentally.

In this work we have investigated the magnetic and structural properties of spin-valve films exchange biased by CoFe/NiMn compared to CoFe/lrMn spin valves. A spin-valve film of structure Ta/NiFe/CoFe/Cu/CoFe/NiMnITa showed a giant-magnetoresistance of 5.5% with a Hex∼850 Oe after annealing. Structural ordering of the NiMn in an fct phase after annealing has been observed using x-ray diffraction, with the data exhibiting pure fct(111) texture. The thermal stability of both the exchange pinning and magnetoresistance of NiMn spin-valves was evaluated. The blocking temperature (Tb) of this film is 400°C, compared to 225°C for IrMn based spin-valve films (IrMn thickness ∼50 Å). Blocking temperature distribution and remnant blocking temperature measurements also suggest that NiMn based spin-valves have far superior pinning stability with temperature than IrMn based spin-valves. Magnetoresistance measurements show a linear decrease with temperature due to electron-phonon scattering with the ∆R/R being reduced by 33% at 150°C (as compared to a 50% decrease for IrMn based spinvalves). Extended annealing at 150°C did not effect spin-valve performance, with ∆R/R and R being constant over 60 hours, suggesting that no appreciable interdiffusion is occurring.

Thin films of lanthanum manganates doped with Ca2+, Sr2+, Ba2+ and Pb2+ have been deposited on Si(100) substrate and their electrical and magnetic properties were discussed with respect to the composition, structure and nature of the dopant. Buffer layers of YSZ and La0.8Al0.2O3 were employed and their effect on the materials was studied. Interesting magnetotransport properties were found in some of the films, where there is a large difference between the insulator-metal transition temperature and a ferromagnetic transition temperature.

The biaxial and uniaxial magnetic anisotropies of epitaxial { 100} oriented La0.7(Sr,Ca)0.3MnO3 films on different substrates and of a sphere-shaped single crystal were measured by torque magnetometry at temperatures ranging from T = 20K to room temperature. In the films the biaxial anisotropy with easy axes <110= dominates and is described by a cubic crystal anisotropy constant ranging up to K1 ≈−104J/m3. The uniaxial anisotropy was |Ku| ≤ 103 J/m3 and is explained by anisotropic stress. In the single crystal the main anisotropy is uniaxial with a hard axis parallel to [ 111], and with an anisotropy constant KR up to 104J/m3. KR was measured in different planes and explained by the rhombohedral lattice distortion. The biaxial anisotropy in the crystal (K1 = −103 J/m3 at T = lOOK) was smaller than in the films. Differences between film and single crystalline behaviour are discussed in terms of crystal structure and lattice constriction.

We are studying ferromagnetic films of cobalt and cobalt - palladium heterostructures fabricated by laser assisted chemical deposition from organometalic compounds. We have developed this one-step deposition technique sufficiently to deposit pure metal features with excellent spatial resolution and in multilayer geometries. From the comparison between the continuous and patterned films we can conclude that the patterning of the films into arrays of discrete micron-scale features has a great influence on the magnetic properties of the films.

The Ni80Fe20/Fe50Mn50,thin film system exhibits exchange bias behavior. Here a systematic study of the effect of atomic-scale thin film roughness on coercivity and exchange bias is presented. Cu (t) / Ta (100 Å) / Ni80Fe20 (100 Å) / Fe50Mno50 (200 Å) / Ta (200 Å) with variable thickness, t, of the Cu underlayer were DC sputtered on Si (100) substrates. The Cu underlayer defines the initial roughness that is transferred to the film material since the film grows conformal to the initial morphology. Atomic Force Microscopy and X-ray diffraction were used to study the morphology and texture of the films. Morphological characterization is then correlated with magnetometer measurements. Atomic Force Microscopy shows that the root mean square value of the film roughness exhibits a maximum of 2.5 Å at t = 2.4 Å. X-ray diffraction spectra show the films are polycrystalline with fcc (111) texture and the Fe50Mn50 (111) peak intensity decreases monotonically with increasing Cu thickness, t. Without a Cu underlayer, the values of the coercivity and loop shift are, Hc = 12 Oe and Hp = 56 Oe, respectively. Both the coercivity and loop shift change with Cu underlayer thickness. The coercivity reaches a maximum value of Hc= 36 Oe at t = 4 Å. The loop shift exhibits an initial increase with t, reaches a maximum value of HP = 107 Oe at t = 2.4 Å, followed by a decrease with greater Cu thickness. These results show that a tiny increase in the film roughness has a huge effect on the exchange bias magnitude.

Co-Ag films prepared by Pulsed Laser Deposition and showing GMR in the as deposited state, have been irradiated by excimer laser: the chemical and structural modification induced by such treatment have been studied by XPS and by atomic force and electron microscopies. The pulsed laser irradiation favors the nucleation of nanosized Co grains at Ag grain boundaries, resulting in an enhancement of the magnetoresistivity at low fields and low temperature. Indeed, after laser treatment, a doubled field sensitivity (δGMR/δH) at T=I0K, with respect to the untreated samples, has been observed. The correlation with the observed magnetic properties variations, is discussed.

Nano-structured Ni80Fe20NCu multilayers were electrodeposited by a newly developed electrodeposition process utilizing a recirculating electrochemical flow reactor. This process, which operates in an inert gas environment, overcomes the limitations of conventional multilayer electrodeposition methods (single and dual bath techniques) by depositing pure magnetic layers without codeposition of the nonmagnetic metal and oxidation of metal interfaces. Structure, corrosion resistance and magnetic properties of electrodeposited NiFe (0 to 100 % Fe) thin film alloys were first investigated. Three different crystal regions, α, mixed α and γ, and γ phases were observed at <50,;50, >50 % Fe in the deposit, respectively. The narrow mixed phase regions was around 50 % Fe compared to 70–80% Fe for bulk alloys. The lattice parameters of electrodeposited alloys exhibited the same trends as bulk alloys. Maximum corrosion resistance was obtained at 50% Fe content in 0.5 M NaCl similar to bulk alloys. The corrosion resistance of the α phase was an order of magnitude less than the γ phase. The magnetoresistance (MR) of electrodeposited NiFe thin film alloys was higher than bulk alloys. Based on these studies, Ni80Fe20/Cu multilayers with individual layer thicknesses ranging from 100 nm to 1.26 μm have been electrodeposited in the recirculating electrochemical flow reactor. The layer thicknesses were precisely controlled by adjusting the amount of charge passed.

In this paper, we report our studies on the growth, structural, magnetotransport and magnetic properties of La1−x,CaxMnO3: Co/Ag. Thin films of these materials were grown in situ on (100) LaAlO3 substrates using a pulsed laser deposition technique. Microstructural characterization carried out on these films show that the films are single phase, textured and smooth. The temperature dependence of resistance of the films in the 10 – 300 K range was examined in zero and applied field using four-probe technique and magnetization measurements were carried out using the quantum design superconducting quantum interference device (SQUID) magnetometer. The MR ratios of La0.7Ca0.3MMnO3, Ag added La0.7CaM0.3MnO3 and Co added La0.7CaM0.3MnO3 films were found to be 200%, 3.4 × 104% and 660% in 5 T and 21%, 435% and 30% in 0.1 T respectively. The enhanced MR ratio in the case of Ag added La0.7Ca0.3MMnO3 films is attributed to the increase in the oxygen content and in the case of Co added La0.7Ca0.3MMnO3, it can be attributed to the Co supplying some additional magnetic field.

Epitaxial films of the fcc metals Al, Au, Ag and Ni were grown by physical vapor deposition on Si and Ge (111), (110) and (100) substrates at different deposition temperatures. The epitaxial relationships and morphological features of these films were characterized by transmission electron microscopy and diffraction in plan view and cross section. Ag formed single crystal films on all substrates at all temperatures. Au and Al could be grown as bicrystals, and under some conditions, Al and Ni grew as tricrystal films. The morphological effects of diffusion at the metal/substrate interface are ascribed to diffusion induced grain boundary migration.

A method of investigating thin film crystallographic texture by electron diffraction is reviewed. The reciprocal lattices of fibrous and lamellar textured thin films are spherical belts around the texture axis. Equations describing the projection of the spherical belts onto the Ewald sphere along the texture axis direction are presented. Based on these equations the geometric and intensity evolution of the electron diffraction patterns with the tilt angle about an arbitrary axis in the film plane can be analyzed in a systematic way. The geometric characteristics of the electron diffraction patterns are then used to derive the texture axis directional index and its angular distribution. The way to determine the equal-intensity circular arcs on the diffraction pattern is also discussed. This method can be applied to both single layered and multilayered thin films of various applications.

The thin films Co81−xCr15PtxTa4 with (0002) crystallographic texture have been sputter deposited with and without substrate bias. The lattice parameter of the thin films has been determined by a combination of x-ray diffraction and electron diffraction techniques. The resolution of the electron diffraction was enhanced by a digital imaging technique. The variation rate of the a lattice parameter with Pt content is consistent with Vegard's law. The change in the c lattice parameter is much greater than what is expected from Vegard's law.

Nanometer thick films are often in a state of high residual stress. This may strongly influence physical properties such as magnetic anisotropy. The aim of our study is to investigate whether the overall stress in multilayers may be tailored via the control of the sputtering parameters or of the individual thicknesses. The coatings investigated were deposited at room temperature by magnetron sputtering on oxidised silicon substrates. Ag/Ni multilayers of superperiod between 4 to 20 nm and thin films (Ag or Ni) 200 nm thick have been deposited under a krypton partial pressure varying between 1 and 8 mTorr. Internal stress measurements were performed by curvature method and x-ray diffraction sin2ψ method. The latter one allows the determination of the stress and of the stress-free lattice parameter in the Ag or the Ni layers whereas the first one gives rise to a measure of the average stress in the coating. The main results are the followings: (i) The stress in Ni thin films changes from compressive to tensile at a pressure between 2 and 5 mTorr whereas Ag thin films are sligthly tensile whatever the pressure; (ii) The stress in multilayers is tensile in Ag and Ni and decreases with sublayer thickness; (iii) The stress free lattice parameter of Ag in thin films or multilayers is independent of the Kr pressure and of the layer thickness and is equal to the bulk value; (iv) On the opposite, the stress-free lattice parameter of nickel decreases with the layer thickness in multilayers and is equal to the bulk value in thin films. These results are discussed in terms of the respective influence of interfacial intermixing and atomic peening mechanism.

We present three dimensional lattice Monte Carlo simulations of sputter deposition onto inclined surfaces. For this purpose, we use a model of an fcc material and we vary the substrate inclination, the texture, and the atomic mobility. In this way we can examine different conditions and mechanisms involved in depositing barrier layer and interconnect films. We obtain results on the density and the roughness of the films. We find that the film texture has dramatic effects on the film density and smoothness. Surprisingly, we find that the surface diffusion coefficients may not be critical parameters; changes in the coefficients by several orders of magnitude may cause only a small change in the film morphology when depositing onto non-wetting substrates.

The evolution of crystallographic texture, grain size and surface morphology in magnetron sputter deposited Al-0.5wt.% Cu polycrystalline thin films is reported as a function of film thickness for SiO2 and SiO2/Ti underlayers for several deposition rates. Regardless of the underlayer type, the initial ≈ 10 nm of the Al-Cu films is nearly randomly oriented, with the films developing a (111) out-of-plane texture which increases in strength with thickness during deposition. The AlCu films on sputtered Ti underlayers developed an exact (111) fiber orientation while Al-Cu films on oxide substrates were offset ≈ 5° from exact fiber orientation. Higher deposition rates were found to result in slightly better (111) textured 20 nm AlCu films. The surface morphology of films, determined by Atomic Force Microscopy (AFM), revealed two regimes of average roughness (Rrms) evolution during deposition. Rrms decreased early in the deposition process, followed by a roughening regime where Rrms increased with thickness. These results are discussed in terms of mechanisms such as grain growth, which help to determine microstructure development during film formation from the vapor.

Ta films were grown using sputter gas (Ar) pressures ranging from 1.7 to 20 mTorr. This produced growth environments where incoming adatom kinetic energies ranged from over 100 eV to less than 1 eV. Film development was monitored in-situ using a x-ray diffraction set-up that allowed complete diffraction patterns to be rapidly collected without interrupting the growth process. Traditional x-ray diffraction methods, transmission electron microscopy (TEM), and transmission electron diffraction (TED) were used to examine film microstructure after growth. It was found that lower Ar pressures, which allow higher adatom kinetic energies, produced films that displayed significant grain growth, texturing, and a smooth surface morphology. Those films grown at increasingly higher Ar pressures displayed smaller grain sizes, less texturing, and increasingly porous microstructures. To further explore this effect, the Ar pressure was varied during deposition for several films. The in-situ probe allowed the effects of each pressure increment to be analyzed and compared with previous x-ray and microscopy results. It was found that the microstructure of any particular film layer depended more on the deposition conditions during its formation rather than the structure or crystallography of previous layers.