A new permanent magnet material: Modified Ca ferrite

An experiment was carried out to investigate the preparation condition of anisotropic Ca system ferrite magnets with optimum magnetic and physical properties. Compositions were chosen according to the formula (CaO.nFe
2
O
3
)
100-x
(La
2
O
3
)
x
, where
x
was varied between 0 and 4.0, and n between 5.5 and 6.25. The optimum condition of making magnets and some properties of a typical specimen are as follows. The preparation condition: composition (CaO.6Fe
2
O
3
)
97
(La
2
O
3
)
3
, semisintering condition 1250°C × 1 h in O
2
gas, sintering condition 1275°C × 0.5 h in O
2
gas. Magnetic properties:
4\piI_{10}k = 4200
G, 4πIr = 4100 G,
I
H
C
= 2100 Oe,
B
H
C
= 2050 Oe,
(BH)_{\max} = 3.5
MG . Oe, Ku = 3.34 × 10
⁶
erg/cc, H
A
= 20.5 kOe,
\sigma_{s} = 64.8
emu/g, Tc = 446°C.