ISSN 10637397, Russian Microelectronics, 2011, Vol. 40, No. 7, pp. 529–532. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © A.M. Alekseev, V.N. Komkov, S.Yu. Krasnoborod’ko, A.B. Shubin, V.I. Shevyakov, 2010, published in Izvestiya Vysshikh Uchebnykh Zavedenii. Elektronika,
2010, No. 6, pp. 63–66.
One of the scanning probe microscopy meth
ods—magnetic force microscopy (MFM), where
cantilevers with a ferromagnet coating are
employed—has become widely used. Interest in
MFM is connected with its unique capabilities pro
viding investigation and modification of magnetic
properties of micro and nanoobjects [1, 2].
Today the method of twopassage measurements
is used in MFM . In the first passage, the cantile
ver scans (in contact or semicontact mode) the stud
ied surface, fixes its relief, and yields the AFM image;
in the second passage, it is removed from the surface
at a certain distance so that only longrange forces
are acting between the probe and the specimen, and
moves repeating the relief of the surface, thus giving
its magnetic image.
In the practice of investigations of magnetic
objects, various longrange electrical forces (such as
Coulomb force between electrostatic charges accu
mulated by the cantilever and the sample at hand)
may have a parasitic influence on the obtained mag
netic image. However, in the literature there is no
information about studies on this effect .
In this paper, the influence of electrical forces on
the results of MSM measurements is investigated.
In order to simulate influence of electrical forces,
we designed a test structure, which is a thinfilmed
nonmagnetic microwire 1
m in width, constituting
a meander, and carrying a current of 1 mA. An AFM
image of a part of the test structure in the meander
region and surface profile along the chosen line are
shown in Fig. 1.
The magnetic field arises around the microwire
with an electrical current. The intensity of the field at
every point between the conductor and the probe is
given in the approximation of an infinite conductor
by the BioSavart law:
is the current,
is the speed of light, and
distance of the probe from the conductor.
At a distance of 100 nm from the test structure, the
magnetic field intensity is ~0.67
T, which is
close to the intensity of the Earth’s magnetic field.
Investigation of the test structure initially was per
formed by the twopassage method. During the sec
ond passage, the MFM image was obtained in a
semicontact mode by mechanical excitation of res
onant oscillations of the cantilever, which was
removed at 100 nm from the test structure; the phase
difference between amplitudes of free oscillations of
the cantilever and oscillations under magnetic influ
ence during the scanning of the object was registered.
The MFM image of the structure and its cross section
along the white line are shown in Fig. 2.
It follows from our results that the magnetic con
trast of the test structure’s image is far higher than the
one estimated theoretically. Moreover, the registered
signal from the neighboring strips was amplified in
both vertical and lateral directions. It proved that the
electrical field generated by the electric current in the
microwire made a significant contribution to the for
Peculiarities of ThreePassage Measurements in Magnetic
A. M. Alekseev
, V. N. Komkov
, S. Yu. Krasnoborod’ko
, A. B. Shubin
and V. I. Shevyakov
ZAO Nanotekhnologiya MDT, Moscow, Russia
Moscow State Institute of Electronic Engineering (Technical University), Zelenograd, Moscow oblast,
Received June 10, 2010
—The method of threepassage measurements in magnetic force microscopy is described, which
yields refined magnetic images of nano and microobjects, and eliminates the possible parasitic influence of
longrange electrostatic forces while obtaining a magnetic image.