6 Molecular Magnetism of Metal Complexes and Light-Induced …
295
Prussian blue is a very informative guide to the assignment of the
57 Fe Mössbauer
spectra in magnetically ordered state for n = 3 and 4. In the case of Prussian blue,
the spin state of the Fe
II site coordinated by six C atoms of cyanide ligands is the
LS state (t
6
2g , S = 0), and that of the Fe
III site coordinated by six N atoms is the HS
state (t
3
2g e
2
g , S = 0). The estimated H int for Fe
II
(t
6
2g , S = 0) and Fe
III
(t
3
2g e
2
g , S = 5/2)
in Fe
III
4
Fe
II
(CN) 6
3
at 1.6 K are 0 and 54.0 T, respectively [30].
57 Fe Mössbauer
paramers of (n-C n H 2n+1 ) 4 N[Fe
II Fe
III (dto) 3 ] (n = 3–6) are listed in Table 6.2.
In order to confirm the ferromagnetic phase transition, we investigated the magnetization as a function of temperature for n = 3–6, which is shown in Fig. 6.28. The
Curie temperature were estimated at 7, (7 and 13), 19.5 and 23 K for n = 3, 4, 5, and
Table 6.2 57 Fe Mössbauer parameters of (n-C n H 2n+1 ) 4 N[Fe II Fe III (dto) 3 ] (n = 3–6)
Doublet
T
(K)
IS (mm s
-1 ) n =
3
4
5 6
QS (mm s
-1 ) n =
3
4
5
6
H int (T) n =
3
4
5
6
(A)
Fe
III S 6
(S = 1/2)
200
77
4
0.35 0.29 0.35 0.31
0.38 0.36 0.39 0.38
0.33 0.33 0.40 0.42
0.38 0.55 0.51 0.56
0.55 0.60 0.68 0.74
0.55 0.51 0.73 0.71
23.4 24.1 24.6 24.8
(B)
Fe
II O 6
(S = 2)
200
77
4
1.14 1.05 1.17 1.14
1.28 1.20 1.24 1.23
1.26 1.26 1.24 1.26
1.43 1.20 1.69 1.24
1.57 1.27 1.84 1.31
1.41 1.41 1.84 1.37
10.2 10.0 7.3 9.9
(C)
Fe
II S 6
(S = 0)
77
4
0.43 0.46 − −
0.43 0.46 − −
0.35 0.41 − −
0.39 0.46 − −
0 0 .. − . . . −
(D)
Fe
III O 6
(S = 5/2)
77
4
0.54 0.55 − −
0.55 0.55 − −
0.89 0.92 − −
0.90 0.95 − −
44.8 44.8 − ... −
Fig. 6.28 Magnetization of (n-C n H 2n+1 ) 4 N[Fe II Fe III (dto) 3 ] (n = 3–6) as a function of temperature.
FCM: field-cooled magnetization, ZFCM: zero-field-cooled magnetization, RM: remnant magnetization. FCM and ZFCM were measured at 3.0 mT. (= 30 Oe). T C and θ denote the Curie temperature
and Weiss temperature, respectively
295
Prussian blue is a very informative guide to the assignment of the
57 Fe Mössbauer
spectra in magnetically ordered state for n = 3 and 4. In the case of Prussian blue,
the spin state of the Fe
II site coordinated by six C atoms of cyanide ligands is the
LS state (t
6
2g , S = 0), and that of the Fe
III site coordinated by six N atoms is the HS
state (t
3
2g e
2
g , S = 0). The estimated H int for Fe
II
(t
6
2g , S = 0) and Fe
III
(t
3
2g e
2
g , S = 5/2)
in Fe
III
4
Fe
II
(CN) 6
3
at 1.6 K are 0 and 54.0 T, respectively [30].
57 Fe Mössbauer
paramers of (n-C n H 2n+1 ) 4 N[Fe
II Fe
III (dto) 3 ] (n = 3–6) are listed in Table 6.2.
In order to confirm the ferromagnetic phase transition, we investigated the magnetization as a function of temperature for n = 3–6, which is shown in Fig. 6.28. The
Curie temperature were estimated at 7, (7 and 13), 19.5 and 23 K for n = 3, 4, 5, and
Table 6.2 57 Fe Mössbauer parameters of (n-C n H 2n+1 ) 4 N[Fe II Fe III (dto) 3 ] (n = 3–6)
Doublet
T
(K)
IS (mm s
-1 ) n =
3
4
5 6
QS (mm s
-1 ) n =
3
4
5
6
H int (T) n =
3
4
5
6
(A)
Fe
III S 6
(S = 1/2)
200
77
4
0.35 0.29 0.35 0.31
0.38 0.36 0.39 0.38
0.33 0.33 0.40 0.42
0.38 0.55 0.51 0.56
0.55 0.60 0.68 0.74
0.55 0.51 0.73 0.71
23.4 24.1 24.6 24.8
(B)
Fe
II O 6
(S = 2)
200
77
4
1.14 1.05 1.17 1.14
1.28 1.20 1.24 1.23
1.26 1.26 1.24 1.26
1.43 1.20 1.69 1.24
1.57 1.27 1.84 1.31
1.41 1.41 1.84 1.37
10.2 10.0 7.3 9.9
(C)
Fe
II S 6
(S = 0)
77
4
0.43 0.46 − −
0.43 0.46 − −
0.35 0.41 − −
0.39 0.46 − −
0 0 .. − . . . −
(D)
Fe
III O 6
(S = 5/2)
77
4
0.54 0.55 − −
0.55 0.55 − −
0.89 0.92 − −
0.90 0.95 − −
44.8 44.8 − ... −
Fig. 6.28 Magnetization of (n-C n H 2n+1 ) 4 N[Fe II Fe III (dto) 3 ] (n = 3–6) as a function of temperature.
FCM: field-cooled magnetization, ZFCM: zero-field-cooled magnetization, RM: remnant magnetization. FCM and ZFCM were measured at 3.0 mT. (= 30 Oe). T C and θ denote the Curie temperature
and Weiss temperature, respectively