Question

State the magnetic properties of nanomaterials.

Answer 1

Magnetic properties of nanomaterials

Let us today discuss the magnetic properties of nanomaterials or nanoparticles. Magnetic nanoparticles are those which can be affected using magnetic field. These particles usually contain magnetic elements like iron, nickel, cobalt etc. Magnetic nanoparticles show a variety of unusual magnetic behaviour when compared to the bulk materials, mostly due to surface or interface effects, including symmetry breaking, electronic environment or charge transfer and magnetic interactions. Let us discuss some other magnetic properties of nanomaterials with examples:

1) The physical and chemical properties of magnetic nanoparticles mainly depend upon the chemical structure and method of synthesis. For example, nano scale particles of magnetite show superparamagnetism at a transition temperature, which is smaller than the transition temperature of bulk material.

2.) Nanocomposite magnets consisting of uniform mixture of magnetically hard and soft phases have been extensively investigated in recent years due to their useful hard magnetic properties.

 

3.) High energy products and relatively high coercivities can be developed in these nanocomposite magnets. These magnets are high value of remanence and low cost.

4.) Magnetic studies in nanostructured materials have focused on the interaction between electron charges and magnetic spins and these studies have led to discoveries of new and unique phenomena that are neither observable in traditional bulk materials, nor explainable using classical theories. For examples: Giant Magnetoresistance (GMR) in multilayers and metallic granular solids, spin valves, spin injection etc.

5.) Magnetostrictive materials are of great scientific importance to us. Magnetostriction is the process in which magnetic material deformed due to presence of magnetic field.

 

6.) Magnetorestrictive nano scale films can allow such functions, which cannot be done using existing integrated circuits. For example these constitute driving elements of micro robots, pumps, motors etc. These can also be used for magnetic control of elastic properties or dependence of stress or strain on magnetic permeability to develop various electronic devices like a resonator with magnetically adjustable frequency and stress controlled inductance.

These are the magnetic properties of nanomaterials, if you know others, then you can share with us.

Answer 2

In small nano clusters the effect of reduced dimensionality on electronic structure has the most profound effect on the energies of highest occupied molecular orbital (HOMO) which is valence band and the lowest unoccupied molecular orbital(LUMO),essentially the conduction band.

The optical emission and adsorption occurs when the transition of the electrons occur between these two states.

Semiconductors and many metals show large changes in optical properties such as color, as a function of particle size.

Colloidal suspenses of gold nano particles have a deep red color which becomes progressively more yellow as the particle size increases.

Gold spheres of 10-20nm exhibit red color

Gold spheres of 2-5nm exhibit yellow color.

Gold spheres of >20nm exhibit purple color