Electricity: measuring and testing – Magnetic – Magnetometers
Reexamination Certificate
2002-05-06
2004-02-24
Le, N. (Department: 2862)
Electricity: measuring and testing
Magnetic
Magnetometers
C324S260000
Reexamination Certificate
active
06696833
ABSTRACT:
Priority is claimed to Patent Application Number 2001-77578 filed in Rep. of Korea on Dec. 8, 2001, herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a microscope for observing a magnetic domain and a method of measuring a magnetic domain, and more particularly, to a Lorentz force microscope and a method of measuring a magnetic domain using Lorentz force.
2. Description of the Related Art
An apparatus for measuring a magnetization state of a micro magnetic domain of a magnetic medium is currently needed in the development of the magnetic medium for storing highly integrated and high density information.
A microscope for observing an existing magnetic medium includes an optical magnetic microscope, a near-field optical microscope, a scanning electron microscope (SEM), magnetic force microscope (MFM), and the like. Among these, the MFM is mainly used to detect the magnetization of a micro magnetic domain and obtain high resolution.
The MFM is an apparatus for detecting the magnetization direction of a magnetic domain of a recording medium using a probe which is coated with a magnetic substance. The MFM operates in a state that it does not contact the magnetic domain. A cantilever of the MFM is affected by an atomic force and a magnetic force at the same time. Atomic force is a short-range force and increases exponentially as the tip-sample distance decreases whereas magnetic force is a long range one and smoothly decreases as tip-sample distance increases. Therefore, topography information is dominantly obtained at short tip-sample distances while magnetic force image is dominantly acquired at long tip-sample distances. As a result, information on the magnetization direction of the magnetic domain of the recording medium can be obtained by scanning the tip both at short and long distances followed by subtracting the two images so obtained.
FIG. 1
is a schematic diagram of a MFM. Referring to
FIG. 1
, a probe
11
of a MFM
10
is coated with a magnetic material
13
. The probe
11
is connected to a cantilever (not shown) to move up and down depending on the direction of each magnetic domain of a magnetic medium
15
. If the tip coating material has downward magnetization direction, the cantilever deflection will be upward when the magnetization of a magnetic domain is in up (↑) direction whereas it will be downward when the magnetization of a magnetic domain is in a down (↓) direction. The magnetization map of the magnetic domains of the recording medium
15
can be detected by stacking the line profile of the cantilever deflection.
However, since a probe of a conventional magnetic medium is coated with a magnetic material, the radius of the probe is large. Also, since the probe reproduces information from the recording medium in a state that it does not contact the recording medium, there is a limit in resolution. Further, the probe may be demagnetized and thus the reliability of the image may decrease.
SUMMARY OF THE INVENTION
To solve the above-described problems, it is an object of the present invention to provide a microscope for reading magnetization directions of magnetic domains of a recording medium in a state that the microscope contacts or does not contact the recording medium to accurately detect the magnetization directions.
Accordingly, to achieve the above object, there is provided a Lorentz force microscope for measuring magnetic domains of a magnetic medium. The Lorentz force microscope includes: a conductive probe which is actuated by Lorentz force occurring due to the interaction between a magnetic field of the magnetic medium and current applied into the magnetic field; a bottom electrode which is prepared on one side of the magnetic medium, for charging the magnetic field with electricity; a scanner for supporting the magnetic medium on which the bottom electrode is prepared and actuating the magnetic medium so that the conductive probe opposite to a record of the magnetic medium scans the record of the magnetic medium; and an information detector for controlling the scanner and detecting information on magnetization of the magnetic medium from motion components of the conductive probe.
The information detector includes: a power supply for supplying power to the conductive probe and the bottom electrode; a light source for radiating light onto the conductive probe to sense the motion components of the conductive probe; a photo diode for converting light reflected on the conductive probe into a photoelectric signal to output a signal with respect to the motion components of the conductive probe; an information output unit for outputting information on magnetization directions of the magnetic medium from the signal output from the photo detector; and a controller for controlling the scanner so that the conductive probe scans the record of the magnetic medium.
It is preferable that the power supply supplies alternating current.
The conductive probe has a tip with a radius of 50 nm or less. The conductive probe is conic, pyramidic, or cylindrical.
To achieve the above object, there is provided a method of measuring magnetic domains using a Lorentz force microscope having a conductive probe which is positioned over a magnetic medium and a bottom electrode which is prepared on one side of the magnetic medium and charges the magnetic medium with electricity. Current is applied to the conductive probe and the bottom electrode when the conductive probe scans a record of the magnetic medium. The conductive probe is oscillated by Lorentz force due to the interaction between the current and a magnetic field of the magnetic medium to scan the record of the magnetic medium. Magnetization directions of the magnetic domains of the magnetic medium are detected from motion components of the conductive probe.
When detecting the magnetization directions of the magnetic domains of the magnetic medium, light is radiated onto the conductive probe and light reflected on the conductive probe is received. Next, directions of Lorentz force which is applied to the conductive probe are detected from the received light signal, and then magnetization directions of the magnetic domains of the magnetic medium are determined based on the detected directions of Lorentz force.
In a Lorentz force microscope and a method of measuring the magnetic domains using Lorentz force, the magnetic domains can be imaged in a state that a probe contacts a magnetic medium. Thus, a magnetization distribution map having improved resolution can be provided. Lorentz force which is horizontal force having low atomic force and crosstalk can be measured. Thus, a magnetization distribution map, which is distinguished from image degree of a record, can be obtained.
Lorentz force is the force that charged particles experience when they move in a magnetic field. In particular, if an electric field and the magnetic field exist at the same time, the force which is applied to the moving charged particles can be represented by Lorentz force equation as seen in equation 1:
{right arrow over (F)}=Q
(
{right arrow over (E)}+
(
{right arrow over (v)}×{right arrow over (B)}
)) (1)
Depending on the direction of the current (or charge movement) and magnetic field, Lorentz force can be adjusted to any direction. Therefore, the resulting Lorentz force can be easily identified by properly designing the current flow (or charge movement) above the magnetic media. For example, if the current flows through the tip and interacts with the surface parallel magnetic field generated from the magnetic medium, the Lorentz force will be normal to the plane surface defined by the current direction and the magnetic field which will either cause torsion or normal force on the probe.
REFERENCES:
patent: 4992659 (1991-02-01), Abraham et al.
patent: 5313451 (1994-05-01), Yagi et al.
patent: 5481527 (1996-01-01), Kasanuki et al.
patent: 5793743 (1998-08-01), Duerig et al.
patent: 6147959 (2000-11-01), Ohyama
Hong Seung-bum
Jeon Jong Up
Shin Hyun-jung
Aurora Reena
Burns Doane , Swecker, Mathis LLP
Le N.
Samsung Electronics Co,. Ltd.
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