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controlled using accurate positioning systems, and the tip can be used to scan the
sample surface in order to image it reconstructing its morphology with nanometer lateral resolution. The availability of such nanocharacterization platforms has
stimulated the development of several AFM-based methods for the qualitative and
quantitative investigation—both single-point measurements at selected location and
mapping on a surface simultaneously to the topographical reconstruction—of different physical properties, e.g., magnetic, electric, mechanical, and thermal [2]. Indeed,
while microscopy techniques based on the interaction between the matter and an
electromagnetic radiation (e.g., optical, electron, or X-ray microscopy) can image
the sample by ‘seeing’ its surface, the sample morphology is reconstructed with
AFM by ‘touching’ the surface with the tip. Therefore, the tip can be used as a
probe to measure a physical signal originating from a nanosized volume of material. Depending on the specific physical properties to be characterized, AFM-based
techniques can use standard AFM tips can be used or require ad hoc realized probes,
e.g., standard tips coated with conductive or magnetic layers. Among the latter techniques, magnetic force microscopy (MFM) is an AFM-based technique proposed in
the the late 1980s [3–6] which enables one to image magnetic domains of a sample using a magnetic tip, i.e., a tip coated with a layer of magnetic material such
as Co or Fe. MFM has been originally employed to study recording media [7, 8],
allowing one to clearly and easily visualize their magnetic domains. Also, comprehensive analytical models have been developed to describe the interaction between
the MFM tip and periodically patterned magnetic materials [9] and the pretty good
qualitative and quantitative agreement with MFM data confirmed this technique as
a powerful method to study magnetic recording media [10–12]. With the advent of
nanotechnology, MFM has been quite naturally proposed for the characterization of
magnetic nanoparticles (NPs) and other nanomaterials [13]. Indeed, MFM has been
considered the par excellence technique for magnetic characterization of nanosized
magnetic materials due to its lateral resolution, imaging capability and the need for a
relatively simple and widespread experimental setup, i.e., a standard AFM apparatus
with slight modifications to feature MFM facility, now routinely included in standard AFM setups. Nevertheless, more recently the awareness of some limitations
in the use of MFM to study magnetic nanomaterials has been gaining a foothold in
the MFM users community. Among these limitations, in particular the presence of
nonmagnetic artifacts in MFM images may lead to misinterpretation of experimental data and severely hamper the use of MFM as an accurate quantitative tool for
magnetic characterizations of materials at the nanoscale.
In this chapter, we review some applications of MFM in the study of magnetic NPs
and magnetic nanomaterials, in particular focusing on current trends, perspectives,
expected innovations, and highlighting the challenges to be taken up and present
limitations to overcome.
D. Passeri et al.
controlled using accurate positioning systems, and the tip can be used to scan the
sample surface in order to image it reconstructing its morphology with nanometer lateral resolution. The availability of such nanocharacterization platforms has
stimulated the development of several AFM-based methods for the qualitative and
quantitative investigation—both single-point measurements at selected location and
mapping on a surface simultaneously to the topographical reconstruction—of different physical properties, e.g., magnetic, electric, mechanical, and thermal [2]. Indeed,
while microscopy techniques based on the interaction between the matter and an
electromagnetic radiation (e.g., optical, electron, or X-ray microscopy) can image
the sample by ‘seeing’ its surface, the sample morphology is reconstructed with
AFM by ‘touching’ the surface with the tip. Therefore, the tip can be used as a
probe to measure a physical signal originating from a nanosized volume of material. Depending on the specific physical properties to be characterized, AFM-based
techniques can use standard AFM tips can be used or require ad hoc realized probes,
e.g., standard tips coated with conductive or magnetic layers. Among the latter techniques, magnetic force microscopy (MFM) is an AFM-based technique proposed in
the the late 1980s [3–6] which enables one to image magnetic domains of a sample using a magnetic tip, i.e., a tip coated with a layer of magnetic material such
as Co or Fe. MFM has been originally employed to study recording media [7, 8],
allowing one to clearly and easily visualize their magnetic domains. Also, comprehensive analytical models have been developed to describe the interaction between
the MFM tip and periodically patterned magnetic materials [9] and the pretty good
qualitative and quantitative agreement with MFM data confirmed this technique as
a powerful method to study magnetic recording media [10–12]. With the advent of
nanotechnology, MFM has been quite naturally proposed for the characterization of
magnetic nanoparticles (NPs) and other nanomaterials [13]. Indeed, MFM has been
considered the par excellence technique for magnetic characterization of nanosized
magnetic materials due to its lateral resolution, imaging capability and the need for a
relatively simple and widespread experimental setup, i.e., a standard AFM apparatus
with slight modifications to feature MFM facility, now routinely included in standard AFM setups. Nevertheless, more recently the awareness of some limitations
in the use of MFM to study magnetic nanomaterials has been gaining a foothold in
the MFM users community. Among these limitations, in particular the presence of
nonmagnetic artifacts in MFM images may lead to misinterpretation of experimental data and severely hamper the use of MFM as an accurate quantitative tool for
magnetic characterizations of materials at the nanoscale.
In this chapter, we review some applications of MFM in the study of magnetic NPs
and magnetic nanomaterials, in particular focusing on current trends, perspectives,
expected innovations, and highlighting the challenges to be taken up and present
limitations to overcome.