μ

2) For A and E ground terms

μ

Do not expect Temperature dependence.

3) For T ground terms with orbital angular momentum contribution

μ

T terms generally show marked Temperature dependence.

The examples that follow are arranged showing the experimentally observed values, the theoretical "spin-only" value and possible variations expected.

A number of the examples involve "alums" where the central Transition Metal ion can be considered to be octahedrally coordinated by water molecules.

V(IV) tetrahedral

80K 300K μ_{s.o.}/B.M. 1.6 1.6 1.73

VCl

V(IV) octahedral

80K 300K μ_{s.o.}/B.M. 1.4 1.8 1.73

Since there is a direct orbital angular momentum contribution we should calculate μ

For a full S+L contribution this would give μ

showing that the magnetic moment is partially quenched.

V(III) octahedral

80K 300K μ_{s.o.}/B.M. 2.7 2.7 2.83

Since there is a direct orbital angular momentum contribution we should calculate μ

For a full S+L contribution this would give μ

So, μ

showing that the magnetic moment is significantly quenched.

In this case, there is no observed Temperature variation between 80 and 300K and it may require much lower temperatures to see the effect?

Cr(III) octahedral

80K 300K μ_{s.o.}/B.M. 3.8 3.8 3.87

Cr(II) octahedral

80K 300K μ_{s.o.}/B.M. 4.8 4.8 4.9

K

Mn(III) low-spin octahedral

80K 300K μ_{s.o.}/B.M. 3.1 3.2 2.83

Since there is a direct orbital angular momentum contribution we should calculate μ

For a full S+L contribution this would give μ

So, μ

showing that the magnetic moment is partially quenched.

In this case, there is a small Temperature variation observed between 80 and 300K.

Mn(II) high-spin octahedral

80K 300K μ_{s.o.}/B.M. 5.9 5.9 5.92

Expect μ

K

Fe(III) low-spin octahedral

80K 300K μ_{s.o.}/B.M. 2.2 2.4 1.73

Since there is a direct orbital angular momentum contribution we should calculate μ

For a full S+L contribution this would give μ

So, μ

showing that the magnetic moment is partially quenched.

Fe(II) high-spin octahedral

80K 300K μ_{s.o.}/B.M. 5.4 5.5 4.9

Since there is a direct orbital angular momentum contribution we should calculate μ

For a full S+L contribution this would give μ

So, μ

showing that the magnetic moment is not showing much quenching.

Co(II) tetrahedral

80K 300K μ_{s.o.}/B.M. 4.5 4.6 3.87

The observed values are somewhat bigger than expected for the small (0.2 B.M.) variation due to equation 2) so other factors must be affecting the magnetic moment. These effects will not be covered in this course!

Co

Co(II) high-spin octahedral

80K 300K μ_{s.o.}/B.M. 4.6 5.1 3.88

Since there is a direct orbital angular momentum contribution we should calculate μ

For a full S+L contribution this would give μ

So, μ

showing that the magnetic moment is not showing much quenching.

Ni(II) octahedral

80K 300K μ_{s.o.}/B.M. 3.3 3.3 2.83

The observed values are somewhat bigger than expected for the small (0.2 B.M.) variation due to equation 2) so other factors must be affecting the magnetic moment. These effects will not be covered in this course!

(Et

Ni(II) tetrahedral

80K 300K μ_{s.o.}/B.M. 3.2 3.8 2.83

Since there is a direct orbital angular momentum contribution we should calculate μ

For a full S+L contribution this would give μ

So, μ

showing that the magnetic moment is partially quenched.

Cu(II) octahedral

80K 300K μ_{s.o.}/B.M. 1.9 1.9 1.73

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