Magnetic Properties of Inorganic Compounds

DATA

Part A. Magnetite Nanoparticles

Table A.1
Magnet
Observations
Neodymium
Multiple spikes were pointing upwards, and outwards. Some spikes are antiparallel.
Alnico
There were two spikes, both pointing upwards.
Magnetic Nanoparticles
Spikes pointed in all directions. The farther the magnet is moved, the bigger the spikes. The closer the magnets were moved, the smaller the spikes.
*For all magnets, the spikes quickly disappeared one the magnet was removed from under the ferrofluid.

Part B.1 Magnetic Susceptibility Measurements of Iron Compounds

Table B.1
Compound
MW (g/mol)
Mass (g)
Length (cm)
R0
R
Paramagnetic/ Diamagnetic
Xg
XM
XMcorr
μeff (BM) n MnSO4∙4H2O
224.00
0.343
3.8
-32
5958
Paramagnetic
6.63x10-5
1.49x10-2
1.50x10-2
5.95
5
K4Fe(CN)6∙3H2O
422.43
0.222
3.4
-27
-47
Diamagnetic
-3.06x10-7
-1.29x10-4
6.00x10-5
0.38
0
K3Fe(CN)6
329.26
0.241
2.6
-28
491
Paramagnetic
5.60x10-6
1.84x10-3
1.98x10-3
2.16
1
FeSO4∙7H2O
278.02
0.233
3.0
-26
2270
Paramagnetic
2.96x10-5
8.22x10-3
8.36x10-3
4.44
4
FeCl3∙6H2O
270.30
0.221
2.7
-27
3360
Paramagnetic
4.14x10-5
1.12x10-2
1.13x10-2
5.18
4
Co(H­2O)6Cl2 (pink)
237.93
0.225
2.6
-29
869
Paramagnetic
1.04x10-5
2.47x10-3
2.61x10-3
2.48
2
Cr compound (purple)
~500.00
0.171
3.1
-27
534
Paramagnetic
1.02x10-5
5.09x10-3
5.34x10-3
3.55
3
Nickel Phosphine (orange)
654.19
0.24
3.0
-23
398
Paramagnetic
5.26x10-6
3.44x10-3
3.84x10-3
3.01
2

Sample Calculations: K3Fe(CN)6

DISCUSSION

Part A.
1. When a magnet is near a ferrofluid, the particles align with the magnetic field. Movement of the magnet causes immediate adjustment of the ferrofluid to the newly positioned magnetic field. This is why the spikes structures were moving when the fluid was tested with a magnet.

2. Ferrofluid are ferromagnetic liquids. Ferromagnetic compounds have permanent magnetic behavior, and all magnetic dipoles are parallel. The ferrofluid observed in this experiment was not permanently magnetic, since the spike structures quickly disappear once the magnet is removed. The fluid was only displayed magnetism when a strong magnetic field was placed near the fluid. In addition, the spike structures were not all parallel to one another, with some pointing outwards while others pointed upwards. This is why the term “ferrofluid” is a misnomer for the liquid.

3. The spinel structure of magnetite consist of Fe2+ and Fe3+ in different pack structures, with the former in tetrahedral arrangement with oxide ions, whereas the latter is in an octahedral arrangement with surrounding oxides. The Fe3+ ions cancel each other out, while Fe2+ ions have a nonzero net magnetic moment. This is why the fluid exhibits ferrimagnetic properties rather than ferromagnetic, because the some magnetic dipoles are antiparallel, but the overall dipole moment is nonzero which is shown by the spikes when magnets are placed near the fluid.

4. Two types of magnets used were Neodymium, an alloy composed of neodymium, iron, and boron, and alnico which is composed of nickel, aluminum, and cobalt. Neodymium has a tetragonal crystal structure whereas alnico has a columnar body center cubic structure. Both structures allow the magnets to have resistance against demagnetization. This is why they are permanent magnets. The nanoparticles are not permanently magnetic after contact with the magnets because of their small size so long range order cannot be permanently induced. The ferrofluid has paramagnetic-like properties in that their magnetic poles are scattered and random naturally, until a magnetic field causes them to line up or “spike”.

Part B.1. Part B of the experiment explores the magnetic properties of known and unknown inorganic compounds by measuring magnetic susceptibility. Iron(II,III) are first examined. In K4Fe(CN)6, the oxidation state of iron is Fe2+. Given that the iron compounds are octahedral complexes, and since CN- is a strong field ligand, the compound is expected to form low