Electricity: measuring and testing – Magnetic – With means to create magnetic field to test material
Reexamination Certificate
2000-03-20
2002-05-28
Patidar, Jay (Department: 2862)
Electricity: measuring and testing
Magnetic
With means to create magnetic field to test material
C324S251000, C324S244000, C324S233000, C324S262000
Reexamination Certificate
active
06396261
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a scanning AC hall microscope, and more particularly pertains to a scanning AC hall microscope which measures the domain pattern of magnetic materials by measuring the oscillatory motion of a domain boundary under the influence of an external applied AC magnetic field, which allows a differentiation between domains which are immobile and domains which are mobile.
The last decade has seen an explosion in the types and techniques used in scanning microscopy in general. Among them is the subfield of scanning magnetic microscopy which provides a spatial image of the magnetic properties of a system under study. Four different types of magnetic microscopes are being used currently: SQUID microscopes, magnetic force microscopes, magnetoresistance microscopes and Hall microscopes.
SUMMARY OF THE INVENTION
Accordingly, it is a primary object of the present invention to provide a scanning AC hall microscope.
In accordance with the teachings herein, the present invention provides a scanning AC Hall microscope and a method of operation thereof which measures the domain pattern of magnetic materials by measuring the oscillatory motion of a domain boundary under the influence of an externally applied AC magnetic field, which allows a differentiation between domains which are immobile and domains which are mobile. A steady DC magnetic field H
0
and an alternating AC magnetic field H
ac
are applied to a sample magnetic material, such that the net magnetic field H(t) seen by the sample magnetic material is
H
(
t
)=
H
0
+H
ac
cos(&ohgr;
t
)
The spatial image of the AC response of the sample magnetic material is detected, by detecting the amplitude of the oscillatory field B
ac
and the phase difference &phgr; as the sample is scanned with a Hall sensor.
REFERENCES:
A.M. Chang, et al., “Scanning Hall Probe Microscopy”, Applied Physics Letters, 61, (1992), 1974-1976.
A. Oral, et al., “Real-Time Scanning Hall Probe Microscopy”, Applied Physics Letters, 69 (1996), 1324-1326.
M. Seul, et al., “Morphology and Local Structure in Labyrinthine Stripe Domain Phase”, Science, 254 (1991), 1616-1618.
T. Garel, et al., “Phase Transitions with Spontaneous Modulation-The Dipolar Ising Ferromagnet”, Physical Review B, 26 (1982) 325-329.
Bhattacharya Sabyasachi
Higgins Mark J.
Martchevskii Maxim
NEC Research Institute Inc.
Patidar Jay
Scully Scott Murphy & Presser
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