Effect of VN buffer layer on the magnetic anisotropy of epitaxial Ni80Fe20thin films deposited on MgO (001) substrates (original) (raw)
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Physical Review B, 2001
The structure and magnetism of epitaxial Ni 80 Fe 20 films grown on stepped and nonstepped Mo͑001͒ planes and MgO͑110͒ substrate have been studied. Single-crystal Ni 80 Fe 20 ͑110͒ films were prepared on MgO͑110͒ substrates. Bi-crystal Ni 80 Fe 20 ͑110͒ films were stabilized on Mo͑001͒ nonstepped planes. On Mo͑001͒ stepped surfaces, interestingly enough, quad-crystal Ni 80 Fe 20 ͑110͒ films with rough surfaces were formed above ϳ200°C and single-crystal Ni 80 Fe 20 ͑001͒ films with smooth surfaces were formed below ϳ100°C. Thick films ͑Ͼ300 Å͒ of single-crystal, bicrystal, and quad-crystal Ni 80 Fe 20 ͑110͒ show uniaxial, biaxial and isotropic magnetic behavior, respectively. The easy axis of the single-crystal Ni 80 Fe 20 ͑001͒ is directed along the Mo step edge direction and the M-H loop along the hard axis reveals a two-step magnetic moment rotation process. The magnetic anisotropies of the Ni 80 Fe 20 films were determined by vibrating sample magnetometer. Details of the epitaxial growth and interplay of structure and magnetism of these Ni 80 Fe 20 films are presented.
Anisotropic Magnetoresistance Evaluation of Electrodeposited Ni80Fe20 Thin Film on Silicon
Micromachines
In this study, a simple growth of permalloy NiFe (Py) thin films on a semiconductive Si substrate using the electrochemical deposition method is presented. The electrodeposition was performed by applying a direct current of 2 mA/cm2 during different times of 120 and 150 s and thin films with different thicknesses of 56 and 70 nm were obtained, respectively. The effect of Py thickness on the magnetic properties of thin films was investigated. Field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), ferromagnetic resonance (FMR), anisotropic magnetoresistance (AMR), and magneto-optic Kerr effect (MOKE) analyses were performed to characterize the Py thin films. It was observed that the coercivity of the Py thin film increases by increasing the thickness of the layer. Microscopic images of the layers indicated granular growth of the Py thin films with different roughness values leading to different magnetic propertie...
Surface morphology, structure and magnetic anisotropy in epitaxial Ni films
Journal of Alloys and Compounds, 2004
Understanding the correlation between film structure and its ferromagnetic properties is very important for applications. To this end, we have investigated epitaxial and smooth Ni films grown on MgO substrates using molecular beam epitaxy (MBE) and dc sputtering. To establish correlation between film morphology and structure with magnetic properties, we have used in situ and ex situ scanning tunneling microscopy (STM) images along with studies on the azimuthal dependence of the magnetization reversal utilizing longitudinal Kerr effect (MOKE). Our MOKE azimuthal studies on annealed MBE-grown (0 0 1) Ni films indicate additional uniaxial anisotropy possibly related to surface nano-patterning, superimposed to the expected four-fold symmetry due to magneto-crystalline anisotropy. This uniaxial anisotropy is absent in non-annealed MBE-grown (0 0 1) Ni films as well as sputtered annealed and non-annealed (0 0 1) Ni films. Conversely, neither annealed MBE-grown nor sputtered (1 1 1) oriented Ni films exhibit surface nano-patterning and their structural and magnetic properties exhibit identical azimuthal dependence.
Journal of Magnetism and Magnetic Materials, 2018
Exchange bias properties of NiFe/FeMn thin films have been investigated through X-ray diffraction, hysteresis loops, angular measurements of anisotropic magnetoresistance (AMR) and magnetic torque. As first predicted by Meiklejohn and Bean we found a decrease on the bias field as the NiFe layer thickness increases. However such reduction is not as strong as expected and it was attributed to the increase on the number of uncompensed antiferromagnetic spins resulting from the increase on the number of FeMn grains at the interface as the thickness of the NiFe layer is increased. The angular evolution of AMR and the magnetic torque were calculated and compared to the experimental ones using the minimization of the free magnetic energy and finding the magnetization equilibrium angle. The free energy, for each grain of the polycrystalline sample, is composed by the following terms: Zeeman, uniaxial, unidirectional and the rotatable energies. While from the AMR curves we obtain stable anisotropy fields independently on the measuring fields, from the torque curves we obtain increasing values of the uniaxial and rotatable fields, as the measuring field is increased. These results were attributed to the physical origin and sensitivity of the two different techniques. Magnetoresistance is mainly sensitive to the inner portion of the ferromagnetic layer, and the torque brings out information of the whole ferromagnetic layer including the interface of the layers. In this way, we believe that the increase in the uniaxial and rotatable values were due to an increase on the volume of the ferromagnetic layer, near the interfaces, which is made to rotate with the measuring field. Studying the rotational hysteresis by both techniques allows to separately obtain the contributions coming from the inner portion of ferromagnetic layer and from the interface.
Ferromagnetic resonance study of thickness-dependent magnetization precession in Ni80Fe20 films
Journal of Applied Physics, 2007
The ferromagnetic resonance (FMR) behaviors for Ni80Fe20 Permalloy films with a wide thickness range from 30to360nm were investigated. The FMR measurements were performed by a vector network analyzer (VNA) technique with scanning frequency at a specified external field. The measured frequency response was fitted well by the theoretical precession conditions. The FMR results show that the effective saturation magnetization, μ0Meff, increases from 1.01to1.36T, while the film thickness varies from 30to360nm. A discontinuous transition is observed at the thickness of 90nm, which corresponds to the transformation boundary of domain wall from Néel to Bloch type in Permalloy films. Meanwhile, the variation of damping coefficient with film thickness also shows a discontinuity at 90nm. For films thinner than 90nm, the dampings vary insignificantly with film thickness. For films thicker than 90nm, the damping coefficient varies linearly with the thickness. The result could be explained by the...
Effect of ultra-thin Cu underlayer on the magnetic properties of Ni80Fe50 / Fe50Mn50 films
MRS Proceedings, 1999
ABSTRACTThe 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 thicknes...
Thickness-dependent magnetic properties of Ni81Fe19, Co90Fe10 and Ni65Fe15Co20 thin films
Journal of Magnetism and Magnetic Materials, 2002
We present results of magnetization and magnetic anisotropy measurements in thin magnetic films of the alloys Ni 81 Fe 19 ; Co 90 Fe 10 and Ni 65 Fe 15 Co 20 that are commonly used in magnetoelectronic devices. The films were sandwiched between layers of Ta. At room temperature the critical thickness for all the films to become ferromagnetic is in the range 11-13 ( A. In Co 90 Fe 10 the coercivity and the anisotropy field both depend strongly on layer thickness. r 0304-8853/02/$ -see front matter r 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 -8 8 5 3 ( 0 2 ) 0 0 5 7 7 -2
Influence of growth orientation on the exchange bias in epitaxial CoMn/Ni80Fe20 films
Journal of Magnetism and Magnetic Materials, 2000
Exchange coupling e!ect has been studied in the as-deposited (1 1 1), twinned (1 1 0) and (2 1 1) oriented CoMn/Ni Fe "lms grown on Mo or Pt seeding layer by molecular beam epitaxy. Uniaxial magnetic anisotropy was observed in all cases mainly due to the epitaxial strain between the Ni Fe and seeding layers. We observed that the exchange bias "eld (coercivity) is relatively large (small) for the (1 1 1) oriented CoMn/Ni Fe "lm compared to those of the twinned (1 1 0) and (2 1 1) samples. The orientational dependence of the exchange coupling e!ect in the as-deposited CoMn/Ni Fe "lm is very similar to that of the FeMn/Ni Fe , where uncompensate plane seems not required for signi"cant exchange bias e!ect, in marked contrast to the case of PtMn/Ni Fe .
Tailoring the magnetic properties of Ni 81 Fe 19 thin films by varying their thickness
Journal of Magnetism and Magnetic Materials, 2017
Ni 81 Fe 19 O y thin films with different thicknesses were obtained by atomic layer deposition. After a thermal reduction process, Ni 81 Fe 19 O y films were converted to their strong Ni 81 Fe 19 ferromagnetic phase, usually known as Permalloy. The different thicknesses were obtained by considering 500, 1000, 1500 and 2000 supercycles, which are defined as a cycle of NiCp 2 /O 3 followed by another cycle of FeCp 2 /O 3. The samples were characterized before and after the thermal reduction process with respect to their crystallinity, morphology and magnetism. In particular, the thermally reduced samples exhibit holes whose sizes increase significantly as the thickness of the samples also increases, affecting their magnetic behaviour. As Permalloy is widely used in many applications, its synthesis through atomic layer deposition is expected to introduce comparative advantages over other synthesis processes, opening up new possibilities for nanoelectronic devices.
A study on the thickness dependence of static and dynamic magnetic properties of Ni81Fe19 thin films
Journal of Magnetism and Magnetic Materials, 2016
A set of Permalloy thin films with thicknesses ranging from 100 nm to 1000 nm have been investigated by in-plane hysteresis loops, magnetic torque, microwave permeability and X-ray diffraction measurements. The frequency evolution of the complex permeability was treated within the Debye relaxation model allowing the obtainment of the resonance frequency, resonance linewidth and the rotational component of the permeability at each applied field. The samples can be separated in three groups according their magnetic properties. Samples with thickness until 150 nm present magnetic properties typical of a system with a well defined in-plane uniaxial anisotropy and just one resonance frequency in the high frequency permeability spectra. Samples with thicknesses above 300 nm present magnetization loops almost isotropic in-plane and two resonance frequencies in the permeability spectra. The samples at the intermediate thickness range present some characteristic from thinner and other of the thicker group. Ferromagnetic resonance and torque measurements have detected the presence of a small uniaxial anisotropy even in the thicker group of samples. The multiple ferromagnetic resonances in the permeability spectra present in the thicker group of samples were treated as non-interacting magnetic systems. These characteristics were attributed to the appearance of stripe domains together with a rotatable anisotropy, due to an out-of-plane magnetization component. The relaxation mechanisms which give rise to the resonance linewidth were discussed considering two possible sources, Gilbert damping and anisotropy dispersion. While the Gilbert damping was almost the same for all samples it was verified the anisotropy dispersion increase with the thickness.