In case your magnetic signals are small, look out for artifacts that might arise from sample handling and/or the materials used to hold samples in a magnetometer. Some useful references on this topic are:

a) M A Garcia et al., "Sources of experimental errors in the observation of nanoscale magnetism", J. Appl. Phys. 105, 013925 (2009); doi: 10.1063/1.3060808

b) L M C Pereira et al 2011 "Practical limits for detection of ferromagnetism using highly sensitive magnetometry techniques", J. Phys. D: Appl. Phys. 44 215001 doi:10.1088/0022-3727/44/21/215001

(SQUID studies)

c) M Sawicki et al 2011 "Sensitive SQUID magnetometry for studying nanomagnetism" Semicond. Sci. Technol. 26 064006 doi:10.1088/0268-1242/26/6/064006

(SQUID studies, and references therein; open access)

There's also a list of presentations on magnetic measurements within the repository of slides on the European School on Magnetism's website:

http://magnetism.eu/esm/repository-topics.html

VSM or SQUID anyone of them can be used, but depends how much is your magnetic moment magnitude. for 10^-6 emu order or less amplitude SQUID is better as VSM is not much sensitive.

Yes. You need to characterize with VSM or SQUID to check the magnetic property.

Of course, I agree Satyendra Pal's comment. Squid is more sensitive than VSM, moreover it depends on the moment of the sample. SQUID is generally used to detect extremely weak signals.

Ya you guys are right....

I totally agree with Satyendra Pal. SQUID is far more sensitive.

SQUID is more sensitive then VSM.

The choice is not always simple. If you need to accumulate a large number of experimental data such as hysteresis loops

at different temperatures, VSM is faster than SQUID (assuming that the sample has a sufficiently strong magnetization). If your sample has a weak magnetization than you have to use SQUID. Too conclude, if you can afford speed use VSM or AGFM; if you have sensitivity issues there is no other option beyond SQUID.

Sometimes another issue with VSM vs. SQUID is the cost. Many VSMs do not require the use of cryogens for operation. Most SQUIDS, to take advantage of their sensitivities are often used in conjunction with large magnetic fields (H>2T). Typically, these higher fields are generated by a superconducting electromagnet. The electromagnet has to be cooled down to low Ts before it can be operated. Quite often LH is required, which is getting more expensive all the time.

In case your magnetic signals are small, look out for artifacts that might arise from sample handling and/or the materials used to hold samples in a magnetometer. Some useful references on this topic are:

a) M A Garcia et al., "Sources of experimental errors in the observation of nanoscale magnetism", J. Appl. Phys. 105, 013925 (2009); doi: 10.1063/1.3060808

b) L M C Pereira et al 2011 "Practical limits for detection of ferromagnetism using highly sensitive magnetometry techniques", J. Phys. D: Appl. Phys. 44 215001 doi:10.1088/0022-3727/44/21/215001

(SQUID studies)

c) M Sawicki et al 2011 "Sensitive SQUID magnetometry for studying nanomagnetism" Semicond. Sci. Technol. 26 064006 doi:10.1088/0268-1242/26/6/064006

(SQUID studies, and references therein; open access)

There's also a list of presentations on magnetic measurements within the repository of slides on the European School on Magnetism's website:

http://magnetism.eu/esm/repository-topics.html

Qd also make a squid vsm

VSM SQUID has its advantages. Just to verify whether the sample is magnetic and finding Tc can be fairly trivial. But if you are looking more than that, then one should be very careful in analyzing the data. Trapped fields can lead to interesting results. though VSM SQUID can be operated much faster, slow scan rates can be better. And added ref by Karl are very important.

first attempt is using a VSM.

Apart from the sensitivity of the device (VSM or SQUID), another important question is what kind of magnetic characterization do you want to perform. If the aim is for example, the measurement of a series of hysteresis loops as a function of temperature in order to show the variation of the coercive field (to deduce from it the blocking temperature if superparamagnetic behaviour is expected), you need high sensitivity in the value of the magnetic field, especially when this value goes below 50 Oe. Therefore, the most adequate device should be the SQUID.

I always use Vibrating Sample Magnetometer (VSM) to characterize my magnetite nanoparticles with success.

Regarding the answer of Karl Sandeman, I recommend the application notes by Prof. McElfresh written for the QD MPMS SQUID system. These have general importance concerning artifacts of magnetic measurements. These notes can be downloaded at http://www.qdusa.com/techsupport/index.html.

Very important for the characterization of magnetic nanoparticles can also be the magnetic field itself -- superconducting coils are not really good to generate small applied fields and there might be also a considerable remanence. Therefore, copper coils may be more suitable for the measurements.

If your experiment is to found magnetic moment in those nanoparticles, I suggest the use of SQUID instead of VSM because the magnetic moment sensibility.

I agree with Pedro Gorria. In my work we used SQUID to measure hysteresis curves vs. temperature to calculate the blocking temperature. The blocking temperature is used to determine if the particles are actually superparamagnetic.

I'd like to make another point. Please do make sure that you have very high quality specimens. Magnetism in gold nanoparticles is highly controversial and there may be serious risk of contamination. Magnetometers (VSM and SQUID) cannot distinguish the sources of the magnetic moments they detect.

X-ray magnetic circular dichroism (using circular polarized synchrotron radiation) is an element specific method for detecting magnetic moments. There are positive reports on gold particles (magnetic response reportedly detected), they are claimed to be due to incorrect evaluations by others.

some recent work:

http://onlinelibrary.wiley.com/doi/10.1002/cphc.201200394/abstract

http://prl.aps.org/abstract/PRL/v109/i24/e247203

Palladium unfortunately is not easily measured by this method, since the relevant L2,3 absorption edges are lying just between the soft and hard x-ray ranges and only few facilities world wide support that energy range with circular polarization and sufficiently elevated magnetic fields.

As far as I remember, superparamagnetic Pd (i.e. with ferromagnetically coupled local atomic moments) is found at very small particle sizes only (http://prb.aps.org/abstract/PRB/v49/i17/p12295_1).

My personal experience is that most chemically stabilizing agents at particle surfaces tend to reduce the moments of the metallic NP. Therefore I'd be most careful to cross check against all potential sources of error when you do detect magnetism in these NP samples. Good luck anyway!!

You need a very sensitive technique so you should use SQUID. You should add an elemental analysis investigation (neutron activation or plasma related techniques) to demonstrate that there are no magnetic impurities.

The best choice is SQUID

Contact indore ugc-dae centrefor a recent apparatus combining fastness of vsm and precision of squid

SQUID is quite expensive technique as compared to VSM. SQUID is prefereable for temperature dependent parameters such as coercivity and blocking temperature. I always prefer VSM.

..

Article Magnetic Gold Nanoparticles in SERS-Based Sandwich Immunoass...

I agree with Gorria

The samples in question is palladium and gold nanoparticles. I guess, the magnetic moment is too small to detect with existing VSMs. SQUID is the ideal choice in this case, as suggested by many of the respondents.

Low temp. measurement is quite important in order to investigate superparamagnetism behavior, antiferromagnetic spin canting phenomena, ... etc. VSM is considered impractical to use due to the amount of LH spent particularly, in extensive investigation. However, MPMs-SQUID is much more commensurate as the LH utilized is within the system and requires no addition of LH which is recycled when needed and thus known as cryo-free. This fact reduces the budget required to carry out magnetic characterization. Besides, impracticality of using VSM arise form the too much technical work needed to begin the experiments as compared to MPMs-SQUID, which is of course time consuming.

I also would like to emphasis on the fact that most of the researchers addressed as regard to sensitivity, nonetheless, this depends on the sample's magnetic signature it contained and VSM in this context showed good work with exception in very weak magnetic materials.

For studying the magnetic properties of nano-particles, the SQUID measurement is the best, as in case of nano-particles the magnetic signal is weak. For studying the ferromagnetic properties in nao-particles, which are covered with the property of super-paramagntism, again the SQUID is the best.

Squid

use VSM this is best it gives both value Ms and magnetic moment and also curve for that

it depends on the magnetic signal, in case of "non magnetic"materials as Pd and Au , the best choice is then the SQUID apparatus.

To improve the measurements one can also made the analysis at subs-ambient temperature. At low analysis temperature sometime VSM could be sufficient.

I think that Squid is the favorable technique to measure the magnetization characteristics and other magnetic parameter for nanoparticles due to its better sensitivity and resolution.