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Dear sir
if we have certain probe with low spring constant (say~ 0.2 N/m) and low res freq (say ~10-15 KHz) with magnetic coatong (Co/Cr), then is it possible to do MFM using these probes as the spring constant and resonant freq matches to contact mode probes????
generally MFM is done in non-contact mode, is it possible to do MFM in contact mode also using above probes?
Hi Sandeep.
MFM in contact mode makes very little sense...when close to the surface, magnetic force are completely swamped by other short range forces. It is necessary to remove the probe form the surface to detect magnetic forces. As John said, removing the probe a SHORT distance, with very flexible levers will be close to impossible in ambient conditions. so then, you have to remove it a LONG way. If you do this, you have two problems, which potentiate each other: 1. The magentic force dies of very quickly with distance, to at a distance, of >200 nm, it will be very weak. 2. Your lever in static mode is probably less sensitive than a resonating lever (looking at phase of oscialltion) to the weak magnetic forces...while being also subject to varying defleciton from other things like temperature, electrostatics, etc, making any other weak forces hard to spot.
Unless there is some particular reason you think this would work, the best thing is to get hold of some "standard" MFM probes from Bruker (liek MESP), and follow a normal protocol, doing "LIFT" mode in tapping. If you want to see the effect of different conditions, yo u could look at my paper: C. S. Neves,et al, Nanotechnology 21 (8), 305706 (2010).
regards,
Pete.
The "Deflection Error" channel is just deflection minus the setpoint. You would use this channel if you wanted to attempt contact mode MFM.
But as Pete has said, contact mode MFM is unlikely to be the best choice. I can't think of any circumstance where it should be preferred to tapping MFM.
Regards,
-Ben
Hi Sandeep,
If you have magnetic probes with a 0.2N/m spring constant, you may still be able to conduct MFM. There are different ways to approach this. MFM is usually conducted by LiftMode which will collect a line of topography data, and then use that information on the following line to maintain a constant tip-sample separation when detecting the magnetic fields.
Typically this is conducted in TappingMode, where the cantilever is oscillated at resonance. However, the resonance will be quite low with these probes, so they will likely not work well in Tapping. You could try, and you will probably have to play with a number of parameters (setpoint, gains, rate, drive frequency, drive amplitude, free air amplitude,…) to get them to work, but it may be worth a try. If you can get them to work, you can then conduct the MFM by putting in a Lift Scan Height of 50nm or so on a smooth sample, and detecting the magnetic domains with the Phase channel.
However, you will likely be forced to run these in contact mode, as you suggested. You can bring up the standard contact mode interface. The Height channel would be collected in contact mode. With a cantilever this soft, it will likely be held on the sample by the adsorbed fluid layer during the LiftMode part of the scan, so it would not break free from the surface with a standard 50nm Lift Scan Height. So, you will need to use the parameter "Lift Start Height" in the Interleave menu to pull the probe away from the surface to break it free from the surface fluid layer. After this motion, it will then move back to the Lift Scan Height to create the MFM scan. So, you might put in 500nm into your Lift Start Height, and then put 50nm into your Lift Scan Height, for instance. In this case, the tip will collect a topography line, then lift 500nm to break free from the surface, and then move back toward the sample to a 50nm lift height to perform the lift scan for the magnetic image. For this method, the MFM image would be collected by looking at the Deflection channel. For MFM, deflection detection will have a lower senstivity than when collected the oscillation signals (Phase or Frequency) as in Tapping. So, your signal by this method will be much weaker, but you can still see domains in some cases.
You might try this first on the MFM tape sample, or some standard, straightforward sample before trying this on an unknown sample. Although the low spring constant is not ideal of MFM, it may still work. A standard MFM probe designed for Tapping will still produce a better image with more signal and easier operation than with a low spring constant cantilever.
I hope this helps.
John
hello John
first of all thakyou very much for the response and sorry for late reply.
As you suggested we tried for MFM in contact mode. we are using multimode V SPM, and while doing in contact mode there is no option for deflection. please let us know how it is possible to enable deflection channel. I asked the same question to the engineer of ICON Analytical ( Indian agent to Bruker) and they replied that it is similar to deflection error. These days instead of "deflection" " deflection error" is there in all new systems? So is true that we can see deflection error signal in place of deflection????
looking for reply in this direction....
Thanks
Sandeep