Propriétés des ferrites de lithium partiellement substitués par l'aluminum destinés aux dispositifs micro-ondes

The properties of lithium-alumina substituted ferrites are intended for microwave devices. It is possible to distinguish two main cases. In the first, the materials are magnetically saturated and in the second, the materials work in the hysteresis loop region. Data on lithium-alumina polycristalline materials from the family Li
2
O; 5(1-
x
) [(1-
y
)Fe
2
O
3
,
y
Al
2
O
3
];
z
MnO
2
; are given,
x
and
z
being chosen to optimize the dielectric properties. At room temperature, as
y
is varied from 0 to 0.20, the properties of these materials vary in the following manner: saturation magnetization 4π Ms, from 3770 to 1340 G; Curie temperature θ
c
from 590 to 430 °C. The coercitive force
Hc
, the squareness ratio
R
, and linewidth
\DeltaH
depend upon the firing conditions and technology chosen. Measured values are in the
Hc
= 1.1- to 2.5-Oe range and
R
= 0.75 to 0.92 range. These properties appear satisfactory for microwave devices and, in particular, for latching devices above
S
-band frequencies.