Tag Archives: magnetic AC mode

Observing single magnetite nanoparticles with a diameter of 10nm by using NANOSENSORS SSS-MFMR AFM probes

In their publication “Understanding electrostatic and magnetic forces in magnetic force microscopy: towards single supermagnetic nanoparticle resolution” Alexander Krivcov, Tanja Junkers and Hildegard Möbius describe methods to suppress capacitive coupling effects in MFM hiding the magnetic signal of magnetic nanoparticles.

During MFM measurements performed in an interleave mode moving the tip at a certain distance to the sample surface the tip is exposed not only to magnetic forces but to electrostatic forces between tip and substrates. In case of analyzing nanoparticles laying on a flat substrate, the electrostatic forces changes noticeably with increasing tip to substrate distance whenever the tip is retracted over a nanoparticle. This capacitive signal may overwhelm the magnetic signal that should be detected instead.

The authors propose several approaches to reduce these capacitive signals. The change in electrostatic forces could be minimized by avoiding retraction of tip over the nanoparticle. Therefore, it is proposed to use interleave linear mode following a linear approximation of the sample surface instead of the interleave lift mode following the sample surface as measured. By that, changes in distance between sample substrate and tip at the nanoparticles are avoided. Moreover, they propose using a substrate with a work function comparable to that of the tip in order to reduce electrostatic forces, in general. By applying an appropriate tip bias remaining electrostatic forces could compensated and further suppressed. Finally, the authors suggest using a tip that is as sharp as possible for decreasing the area of the capacitor and NANOSENSORS SSS-MFMR probes are the best choice for this.

The impact of the above mentioned optimizations have been validated experimentally by the authors. Finally, it turned out that if using super sharp magnetic tips further methods suppressing capacitive effects were not necessary. The authors were able to detect superparamagnetic nanoparticles at the single particle level on copper substrate with a NANOSENSORS SSS-MFMR probe without using additional parameters as e. g. tip bias or external magnetic field.Figure 12 from: A. Krivcov et. al, Understanding electrostatic and magnetic forces in magnetic force microscopy: towards single supermagnetic nanoparticle resolution: Figure 12. (a) topography of copper substrate with single magnetite nanoparticle; (b) phase image in 11 nm lift height with an attraction at the place of the nanoparticle; (c) Cross section of a single magnetite nanoparticle (dotted line in (a)) with 10 nm diameter taken on copper substrate with NANOSENSORS SSS-MFMR AFM probe

Figure 12  from: A. Krivcov et. al, Understanding electrostatic and magnetic forces in magnetic force microscopy: towards single supermagnetic nanoparticle resolution: Figure 12. (a) topography of copper substrate with single magnetite nanoparticle; (b) phase image in 11 nm lift height with an attraction at the place of the nanoparticle; (c) Cross section of a single magnetite nanoparticle (dotted line in (a)) with 10 nm diameter taken on copper substrate with SSS-MFMR tip

A. Krivcov, T. Junkers, and H. Möbius
Understanding electrostatic and magnetic forces in magnetic force microscopy: towards single superparamagnetic nanoparticle resolution
J. Phys. Commun., vol. 2, no. 7, p. 075019, 2018
DOI: https://doi.org/10.1088/2399-6528/aad3a4

The article “Understanding electrostatic and magnetic forces in magnetic force microscopy: towards single superparamagnetic nanoparticle resolution” by A. Krivcov, T. Junkers, and H. Möbius is licensed under the Creative Commons Attribution 3.0 License. To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0.

MAC Mode Cantilevers for Keysight, Agilent and Molecular Imaging AFMs now available from NANOSENSORS

Do you have a Keysight, Agilent or Molecular Imaging Atomic Force Microscope in your lab? Are you using MAC Mode (Keysight Technologies’ patented magnetic AC mode ) to image soft samples or for imaging in fluids?
Then NANOSENSORS™ has the right cantilevers for you.

MAC mode imaging of lambda phage DNA in a buffer solution. Image courtesy of Keysight Technologies
MAC mode imaging of lambda phage DNA in a buffer solution. Image courtesy of Keysight Technologies

On the NANOSENSORS Special Developments List you will find all the cantilevers you need to continue working with MAC Mode.

Keysight TYPE II MAC Levers (PN: N9812x) – NANOSENSORS special development code: SD-MAC-Type2

Keysight TYPE VII MAC Levers (PN: N9866x) – NANOSENSORS special development code: SD-MAC-Type7

Keysight TYPE VIII MAC Levers (PN: N9867x) – NANOSENSORS special development code: SD-MAC-Type8

Keysight TYPE IX MAC Levers (PN: N9811x) – NANOSENSORS special development code: SD-MAC-Type9

MAC Mode Cantilevers for Keysight, Agilent and Molecular Imaging Atomic Force Microscopy
MAC Mode Cantilevers for Keysight, Agilent and Molecular Imaging Scanning Probe Microscopes

NANOSENSORS™ launches new Silicon MFM Probe Series

NANOSENSORS™ has launched a new Silicon MFM Probe Series today.

For visualisation of magnetic domains by scanning probe microscopy different magnetic force microscopy probes are necessary.

NANOSENSORS™ Silicon MFM Probes are based on the well-known PointProbe® Plus AFM probe. The probes are optimized in view of high sensitivity and enable Tapping Mode, Non-contact and lift mode operation in air. They are designed to match the demands of a wide range of applications defined by the variety of magnetic samples with different properties. All the different magnetic coatings of the probes show an excellent long-term stability.

The NANOSENSORS™ Silicon MFM Probe Series offers six different types of MFM Probes:

1. PPP-MFMR – Standard Magnetic Force Microscopy Probe

This standard probe for magnetic force microscopy provides a good sensitivity, resolution and coercitivity. The hard magnetic coating on the tip is optimized for high magnetic contrast and high lateral resolution.

Stable imaging of a variety of samples such as different recording media has been demonstrated with this probe.

Typical Values:
Force Constant: 2.8 N/m
Resonance Frequency: 75 kHz
Tipside Coating.: Hard Magnetic
Coercivity: 300 Oe
Magnetisation: 300 emu/cm³
Magnetic Tip Moment: ~ 10^13 emu
Guaranteed Tip Radius: < 50 nm
Achievable Lateral Resolution: < 50 nm

 

2. PPP-LM-MFMR – Low Momentum Magnetic Force Microscopy Probe This AFM probe is designed for reduced disturbance of the magnetic sample by the tip and for enhanced lateral resolution compared to the standard PPP-MFMR probe.

Typical Values:
Force Constant: 2.8 N/m
Resonance Frequency: 75 kHz
Tipside Coating.: Hard Magnetic
Coercivity: 250 Oe
Magnetisation: 150 emu/cm³
Magnetic Tip Moment: x0.5
Guaranteed Tip Radius: < 30 nm
Achievable Lateral Resolution: < 35 nm

 

3. PPP-LC-MFMR – Low Coercivity Magnetic Force Microscopy Probe

This AFM tip is coated with a soft magnetic thin film enabling the measurement of magnetic domains within soft magnetic samples. Due to the low coercivity of the tip coating the magnetisation of the tip will easily get reoriented by hard magnetic samples.

Typical Values:
Force Constant: 2.8 N/m
Resonance Frequency: 75 kHz
Tipside Coating.: Soft Magnetic
Coercivity: 0.75 Oe
Magnetisation: 225 emu/cm³
Magnetic Tip Moment: x0.75
Guaranteed Tip Radius: < 30 nm
Achievable Lateral Resolution: < 35 nm

 

4. SSS-MFMRSuperSharpSilicon™ High Resolution Magnetic Force Microscopy Probe

This MFM probe was especially designed for high resolution magnetic imaging. The well-known NANOSENSORS™ SuperSharpSilicon™ tip is used as a basis and is combined with a very thin hard magnetic coating. This results in an extremely small tip radius and a high aspect ratio on the last few hundred nanometers of the tip apex – the essential requirements for high lateral resolution down to 20 nm in ambient conditions.

Typical Values:
Force Constant: 2.8 N/m
Resonance Frequency: 75 kHz
Tipside Coating.: Hard Magnetic
Coercivity: 125 Oe
Magnetisation: 80 emu/cm³
Magnetic Tip Moment: x0.25
Guaranteed Tip Radius: < 15 nm
Achievable Lateral Resolution: < 25 nm

 

5. SSS-QMFMR – SuperSharpSilicon™ High Resolution Magnetic Force Microscopy Probe with a high Q-factor

This special version of the high resolution magnetic force microscopy probe was especially tailored for applications in UHV. The high resolution and the magnetic characteristics are identical to the properties of the SSS-MFMR. Additionally it achieves a typical Q-factor of over 35 000 under UHV conditions.

Typical Values:
Force Constant: 2.8 N/m
Resonance Frequency: 75 kHz
Tipside Coating.: Hard Magnetic
Coercivity: 125 Oe
Magnetisation: 80 emu/cm³
Magnetic Tip Moment: x0.25
Guaranteed Tip Radius: < 15 nm
Achievable Lateral Resolution: < 25 nm
UHV Quality Factor: > 30 000

 

6. PPP-QLC-MFMR – Low Coercivity Magnetic Force Microscopy Probe with a high Q-factor – for applications in UHV

Like the PPP-LC-MFMR this AFM tip is coated with a soft magnetic thin film enabling the measurement of magnetic domains within soft magnetic samples. Additionally it offers a Q-factor typically higher than 35 000 und UHV conditions.

Typical Values:
Force Constant: 2.8 N/m
Resonance Frequency: 75 kHz
Tipside Coating.: Soft Magnetic
Coercivity: 0.75 Oe
Magnetisation: 225 emu/cm³
Magnetic Tip Moment: x0.75
Guaranteed Tip Radius: < 30 nm
Achievable Lateral Resolution: < 35 nm
UHV Quality Factor: > 30 000

 

For further information please refer to the MFM Probe Series flyer.