For a particular bond, bending and stretching vibration modes show different IR absorption.

You may go through the good articles related to iron oxide vibration modes.

You can read about characteristic peaks of Fe3O4 nanoparticles in my work as well as about changes induced by different size of these nanoparticles (visible shift in FTIR spectrum).

Article Structure and optical properties of Fe 3 O 4 nanoparticles s...

Hi Abhishek,

There are several types of iron oxide like Fe2O3, Fe3O4 etc,. Depending on the compositions, the peak intensity and position varies. Usually metal oxide peaks arise below 1000.

If you peaks are deviating little from the literature, it is accepted.

Hope it helps

As explained above, IR indicates the vibrations of bonded atoms, whether its stretching or bending the value will differ...While looking at iron oxide, look for Fe-O bonding vibrations...as there are different kinds of oxide as per the iron valency, you also can check whether there are any metal-metal bonding, if any... Fe-C and so on...you have to do additional analysis to confirm the groups such as raman or Mass

As mentioned above, iron has more than one oxidation state and it is possible your particles have mixed phases. Additionally, many synthesis methods result in retained chemical species from the precursors and/or solvent used. I would suggest using a complimentary technique like XPS to obtain the elemental composition and the different binding energies of the elements to help determine what the different FTIR vibration modes correlate with.

Abhishek .. you can check first wich kind of magnetic nanoparticles you have by XRD and then your IR will be easier to analyze.