23 Ni Addition Induced Changes in Structural, Magnetic, and Cationic. . .
367
Fig. 23.3 Variation of room
temperature magnetization
with applied magnetic field
-40000 -20000
0
20000 40000
-80
-60
-40
-20
0
20
40
60
80
x = 0.00
x = 0.15
x = 0.45
x = 0.60
x = 0.75
x = 0.30
Magnetisation (Am 2
/kg)
Magnetic Field (Oe)
Table 23.5 Variation of magnetic parameters: Néel and experimental magnetic moment (n e N ,
n e B ) μ B , saturation magnetization (M s ), and Yafet-Kittel angle (α Y-K ) with Ni content (x) for
Zn 0.75−x Ni x Mg 0.15 Cu 0.1 Fe 2 O 4 (ann. 500 ◦ C/3 h) system
x
n e N (μ B )
n e B (μ B )
M s (Am 2 /Kg)
α Y-K (degree)
0.00
1.20
1.14
27.22
7.48
0.15
2.30
2.11
50.49
13.38
0.30
2.50
2.35
56.41
11.52
0.45
2.98
2.90
69.78
7.78
0.60
2.80
2.58
62.55
13.60
0.75
1.90
1.49
36.11
19.93
Perusal of Table 23.5 shows that Néel and experimental magnetic moment
(calculated by using the expression [13]) and saturation magnetization initially
enhance with Ni content up to x = 0.45 and then decrease for 0.45 < x ≤ 0.75,
accredited to the occupation of cations as also explained earlier in [22–24, 51].
Magnetization of Zn-Ni-Mg-Cu ferrite mainly resides on the Ni 2+ (2μ B ) and Fe 3+
(5μ B ) ions because Zn 2+ and Mg 2+ ions are diamagnetic with 0 magnetic moment,
and the percentage of occupied Cu 2+ (1μ B ) ions is constant at B site as the dopant
(Ni(x)) is introduced in the spinel structure. With increasing Ni, up to = 0.45,
Ni 2+ ions force Fe 3+ ions to migrate from A to B site; thus, Fe 3+ ions on B site
increase which in turn increase B site magnetic moment (M B ) and decrease A
site magnetic moment (M A ), and therefore, the magnetization increases. Thus the
saturation magnetization of Zn-Ni-Mg-Cu ferrite linearly depends on the content of
Fe 3+ ions on B site (shown in Fig. 23.4). Highest value of magnetization (69.78
Am 2 /kg) is obtained for x = 0.45. When Zn 2+ are completely substituted by Ni 2+
ions (for x = 0.75), Ni 2+ ions push Fe 3+ ions from B to A site, resulting in decrease
of M s of the system.