1. Magnetism

2. Overview of magnetic materials

3. Magnetic objects

4. Magnetic field lines

5. Molecular magnetism, example 1
Paramagnets are attracted to magnetic fields

6. Paramagnetic gases

7. Organic radicals are magnetic

8. Zeeman splitting and NMR
gap = g mz B
g = Lande g-factor (~2 for eˉ)
mz = magnetic moment
B = magnetic field strength
Nuclear gap energy corresponds to radio frequencies
Certain nucleii have a magnetic spin, and are therefore active in NMR experiments

9. Metals
Many metals have unpaired electrons due to the high d-orbital degeneracy.
n = 3 unpaired spins
S = 3/2 magnetic moment
octahedral Cr3+ has 3 d-electrons

10. Metals
Multiple spin arrangements (HS, LS) are possible for a given number of d-electrons (in this case, 7 valence electrons).
n = 3 unpaired spins
S = 3/2 magnetic moment
n = 1 unpaired spins
S = 1/2 magnetic moment
halides < OHˉ < C2O42- < H2O < NCSˉ < py < NH3 < en < phen < NO2ˉ < CNˉ < CO

11. Zeeman splitting and NMR
gap = g mz B
g = Lande g-factor (~2 for eˉ)
mz = magnetic moment
B = magnetic field strength
Nuclear gap energy corresponds to radio frequencies
Certain nucleii have a magnetic spin, and are therefore active in NMR experiments

12. paramagnet (disordered spins) ferromagnet (co-aligned spins)
antiferromagnet (anti-aligned spins)

13. Ferromagnets have a persistent moment, even without a magnetic field

14. cM vs T for ferromagnets
ferromagnetic
paramagnetic

15. The math of magnetism cM – Molar susceptibility
meff – Effective moment
mB – Bohr magneton

16. Useful experimental quantity
Molar magnetic susceptibility, cM
Magnetic susceptibility per mole
Why use “molar” and not the “gram” susceptibility?

17. Moment per metal atom S = total spin (1/2 per e ˉ) n = # unpaired eˉ
meff = moment in Bohr magnetons (mB)
g = magnetogyric ratio (Landé g-facor, ~2)
mB = 9.27 x J / T

18. Magnetic susceptibility, cM
(Curie Law – assumes no spin-spin interactions)
cM = measurable quantity (M / H)
Can calculate meff from cM
Can calculate # of unpaired electrons from meff
(units are slightly fudged)

19. Magnetic susceptibility, cM
(Curie Law)
Simple approximations break down when spins are not isolated from each other
(Curie-Weiss law)