Micromagnetics of longitudinal recording media

1991 ◽  
Vol 49 ◽  
pp. 754-755
Author(s):  
P.S. Alexopoulos
Keyword(s):  
Thin Films ◽  
Areal Density ◽  
Magnetic Thin Films ◽  
Detailed Knowledge ◽  
Magnetic Storage ◽  
Storage Devices ◽  
Lorentz Microscopy ◽  
Transition Zones ◽  
Wall Structures ◽  
Deposition Parameters

Future needs in high density magnetic storage devices require increases both in linear and track densities. The latest 1 Gigabit per square inch areal density for longitudinal media demonstrated by IBM has reduced the bit size to dimensions comparable to the characteristic micromagnetic length scales of todays media. Improvement or extension of the current recording limits requires detailed knowledge of micromagnetics and their manipulation or tailoring through the microstructure of the utilized magnetic thin films. There is a number of ways that these parameters can be controlled through the microstructure of the thin films including: chemical alloying, use of nucleating underlayers, and deposition parameters. Our investigation of written transitions recorded on a series of cobalt based alloys using Lorentz microscopy showed that the domain wall structures observed in the transition zones are very complex (Figure 1). The transition zones contain not only zig-zags shape 180° walls but also vortex structures and intermediate states between the two.

Structural Study of Iron Oxide Thin Films Using Pre-Edge Feature of XANES

2015 ◽  
Vol 1098 ◽  
pp. 58-62
Author(s):  
Sunil Dehipawala ◽  
Pubudu Samarasekara ◽  
Rasika Dahanayaka
Keyword(s):  
Thin Films ◽  
Magnetic Thin Films ◽  
Peak Position ◽  
Small Scale ◽  
Magnetic Storage ◽  
Energy Position ◽  
Edge Structure ◽  
Storage Devices ◽  
Number Of Layers ◽  
Edge Feature

Recently there has been a very high demand for small scale magnetic storage devices. The industry sector has consistently demanded sub micron or even nanometer scale magnets. Magnetic thin films often contain several layers of coating. For the purpose of this study, we prepared thin film magnets by spin coating a precursor containing iron into a glass substrate. The thickness of the films was controlled by the spin rate. Precursor films on the substrate were then annealed to 6000 C for 3 hours in air. The micro structure of iron in the films was investigated using the pre-edge feature that appears in the X-ray Absorption Near Edge Structure (XANES) for samples containing different iron layers. The main absorption edge peak position and pre-edge energy position were identical in all of the samples. This indicates that there was no change in the charge state of the iron regardless of the number of layers. However the intensity of the pre-edge feature decreases as number of layers increases which shows a decrease of Fe-O compounds as the number of layers increases.

Studies of magnetic structure of written bits using Lorentz microscopy

1989 ◽  
Vol 47 ◽  
pp. 566-567
Author(s):  
T.A. Nguyen ◽  
P.S. Alexopoulos ◽  
S.E. Lambert ◽  
I.L. Sanders ◽  
C. Hwang
Keyword(s):  
Magnetic Structure ◽  
Magnetic Layer ◽  
Information Storage ◽  
Detailed Knowledge ◽  
Magnetic Media ◽  
Lorentz Microscopy ◽  
Magnetic Structures ◽  
Transition Zones ◽  
Size Limits ◽  
Fringing Fields

Understanding the fundamental size limits of magnetic bits for high density information storage requires detailed knowledge of the magnetic structure of the written bits. Bit definition, fringing fields and magnetic structures at and between transition zones are important information for the design of future magnetic media. Using Lorentz microscopy, we have investigated these parameters in Co-alloy thin films as a function of recording density (200, 600 and 1000 fc/mm) on discrete tracks of widths from 0.6 to 10 μm.The magnetic media consist of a Co-alloy and an underlayer prepared by sputtering onto a sputter-cleaned Si disk. The magnetic parameters for the magnetic layer are: coercive field Hc = 950 Oe, remanent magnetization Mr = 533 emu/cm3 and media thickness d = 400 Å. The discrete tracks were formed on the surface of the disk by sputter-etching through a photoresist mask to remove media between the tracks. This permits the recording characteristics of tracks as narrow as 0.6 μm to be investigated using heads of conventional width.

Some Aspects of Deposition Parameters of RF Sputtered Ferromagnetic Film Germane to the Study of Magnetoresistive Sensing Devices

2011 ◽  
Vol 264-265 ◽  
pp. 160-165 ◽  
Author(s):  
Pervez Akhtar ◽  
Tariq Javid Ali ◽  
Arshad Aziz
Keyword(s):  
Thin Films ◽  
Anisotropy Field ◽  
Ferromagnetic Film ◽  
Magnetic Thin Films ◽  
Magnetic Films ◽  
Sputter Deposition ◽  
Deposition Condition ◽  
Magnetic Field Sensors ◽  
Deposition Parameters ◽  
Materials Used

The paper describes results of investigation on sputtered NiFe Films to determine the sputter deposition condition that could produce magnetic field sensors with the desired magnetic and magnetoresistive properties. The magnetic thin films materials used in such devices should have a low coercive force, a low anisotropy field and low magnetization dispersion, α50 with high magnetoresistance ratio. From the results presented, it is shown that that the most useful films for 82%Ni-Fe composition are produced at 200 °C-250 °C moderate substrate temperatures. It is also possible to specify the substrate bias potential and sputter gas pressure sputter deposition conditions under which the 82%Ni-Fe thin films may be employed for the production of magnetoresistine sensors with near optimum magnetic and magnetoresistive properties. The work also provide understanding of the effects on the magnetic properties of sputtered magnetic films that is very limited as current literature is almost entirely limited to evaporated magnetic films.

Conventional methods of Lorentz microscopy

1990 ◽  
Vol 48 (4) ◽  
pp. 756-757
Author(s):  
H.Roy Geiss
Keyword(s):  
Thin Films ◽  
Electron Beam ◽  
Vector Potential ◽  
Magnetic Thin Films ◽  
Incident Electron ◽  
Objective Lens ◽  
Zero Field ◽  
Magnetic Vector Potential ◽  
Lorentz Microscopy ◽  
Incident Electron Beam

Lorentz electron microscopy has been used to study magnetic domain/domain wall structures in thin films since 1959. Initially the contrast was described in terms of the classical Lorentz deflection of the incident electron beam. As a result Lorentz microscopy has become the general designation given to any of the techniques used to study the magnetic structure with electron beams. However, when sufficiently weak interactions are considered, a more rigorous quantum-mechanical description of the electron-specimen is required. It thus becomes necessary to consider the basis of magnetic imaging as following from the interaction between the magnetic vector potential of the specimen and the incident electron beam. This interaction results in a phase change of the propagating electron beam which is proportional to the path integral of the vector potential. Thus Lorentz microscopy, in reality, is simply phase contrast microscopy for a special class of objects.For many of the magnetic thin films investigated the coercivity of the film is so low that it must be in a nearly zero field environment in order to retain the domain structure. In order to achieve this condition experimentally, the objective lens is usually turned off and the diffraction lens is used as the image forming lens.

Simulation of Magnetic Induction Mapping in the TEM

1997 ◽  
Vol 3 (S2) ◽  
pp. 1157-1158
Author(s):  
J. Dooley ◽  
M. De Graef
Keyword(s):  
Objective Lens ◽  
Magnetic Storage ◽  
Experimental Conditions ◽  
Storage Devices ◽  
Lorentz Microscopy ◽  
Full Characterization ◽  
Thin Foils ◽  
Free Region ◽  
High Resolution Tem ◽  
Field Free Region

The design of modern magnetic storage devices with their rapidly increasing information density ne-cessitates a full characterization of the underlying microstructure of the device materials. Lorentz microscopy has for several decades been the main vehicle for micro-magnetic observations. The pri-mary limitation of the Lorentz modes is perhaps the attainable magnification. To avoid saturation, the sample must be placed in a low-field or preferably field-free region in the column, and this invariably means that the microscope can only be operated at low magnifications. Both Fresnel and Foucault images are rather sensitive to the exact experimental conditions which renders quantitative observa-tions quite difficult, if not impossible. Inelastic scattering further limits the usefulness of Lorentz observations to very thin foils.We have recently reported1 a novel Lorentz microscopy setup, combining a Gatan Imaging Filter (GIF) and a JEOL 4000EX top-entry high resolution TEM, operated at 400 kV with the main objective lens switched off.

Lorentz Microscopy in the Study of Magnetic Thin Films

2004 ◽  
Vol 10 (S02) ◽  
pp. 42-43
Author(s):  
Stephen McVitie
Keyword(s):  
Thin Films ◽  
Magnetic Thin Films ◽  
Lorentz Microscopy

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

Temperature Dependence of Magnetic Domains and Wall Structures

1972 ◽  
Vol 30 ◽  
pp. 496-497
Author(s):  
Sonoko Tsukahara ◽  
Tadami Taoka ◽  
Hisao Nishizawa
Keyword(s):  
Temperature Dependence ◽  
Domain Walls ◽  
Magnetic Domain ◽  
Iron Film ◽  
Objective Lens ◽  
Lorentz Microscopy ◽  
Domain Structures ◽  
Wall Structures ◽  
Crystal Films ◽  
Metallurgical Structure

The high voltage Lorentz microscopy was successfully used to observe changes with temperature; of domain structures and metallurgical structures in an iron film set on the hot stage combined with a goniometer. The microscope used was the JEM-1000 EM which was operated with the objective lens current cut off to eliminate the magnetic field in the specimen position. Single crystal films with an (001) plane were prepared by the epitaxial growth of evaporated iron on a cleaved (001) plane of a rocksalt substrate. They had a uniform thickness from 1000 to 7000 Å.The figure shows the temperature dependence of magnetic domain structure with its corresponding deflection pattern and metallurgical structure observed in a 4500 Å iron film. In general, with increase of temperature, the straight domain walls decrease in their width (at 400°C), curve in an iregular shape (600°C) and then vanish (790°C). The ripple structures with cross-tie walls are observed below the Curie temperature.

Observations on the growth of YBa2Cu3O7-δ thin films on MgO by pulsed-laser ablation

1991 ◽  
Vol 49 ◽  
pp. 1068-1069
Author(s):  
M. Grant Norton ◽  
C. Barry Carter
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Laser Ablation ◽  
Substrate Surface ◽  
Pulsed Laser ◽  
Pulsed Laser Ablation ◽  
Thin Film Deposition ◽  
Film Deposition ◽  
Laser Ablation Process ◽  
Deposition Parameters

Pulsed-laser ablation has been widely used to produce high-quality thin films of YBa2Cu3O7-δ on a range of substrate materials. The nonequilibrium nature of the process allows congruent deposition of oxides with complex stoichiometrics. In the high power density regime produced by the UV excimer lasers the ablated species includes a mixture of neutral atoms, molecules and ions. All these species play an important role in thin-film deposition. However, changes in the deposition parameters have been shown to affect the microstructure of thin YBa2Cu3O7-δ films. The formation of metastable configurations is possible because at the low substrate temperatures used, only shortrange rearrangement on the substrate surface can occur. The parameters associated directly with the laser ablation process, those determining the nature of the process, e g. thermal or nonthermal volatilization, have been classified as ‘primary parameters'. Other parameters may also affect the microstructure of the thin film. In this paper, the effects of these ‘secondary parameters' on the microstructure of YBa2Cu3O7-δ films will be discussed. Examples of 'secondary parameters' include the substrate temperature and the oxygen partial pressure during deposition.

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