Influence of Ball Milling Process on the Micro-Morphology and Magnetic Properties of M-Type Hexagonal Ferrites

Conventional yttrium iron garnet-based circulators require the use of an external magnet to provide the biasing field. Hexagonal ferrites with uniaxial anisotropy can avoid the use of external magnets to achieve the self-biasing function, thereby significantly reducing the size, weight, and cost of the circulator. In order to realize the self-biasing function, modulating the hexagonal ferrite so that it has a high remanent magnetization ratio
$(\boldsymbol{M}_{\mathbf{r}}/\boldsymbol{M}_{\mathbf{s}})$
, controllable magnetization strength
$(\boldsymbol{M}_{\mathbf{s}})$
and coercivity
$(\mathbf{H}_{\mathbf{c}})$
is an urgent problem. In this work, Ba
0.9
La
0.1
Fe
11.9
Mn
0.1
O
19
was prepared by solid-phase method, and the changes of its magnetic properties at different ball milling rates were firstly explored. On the basis of the determined ball milling rate, the factor of ball milling time was continued to be added. The magnetic properties of Ba
0.9
La
0.1
Fe
11.9
Mn
0.1
O
19
were modulated by the combination of ball milling rate and time process, and its
$\boldsymbol{M}_{\mathbf{r}}/\boldsymbol{M}_{\mathbf{s}}$
could be increased from the initial 0.804 to 0.885.
$\mathbf{H}_{\mathbf{c}}$
fluctuated between 2.07-2.94 KOe, and the corresponding
$\boldsymbol{M}_{\mathbf{s}}$
increased from 58.31 emu/g to 66.83 emu/g. The best overall performance was achieved at ball milling time and rate of 18 h and 33 Hz, respectively:
$\boldsymbol{M}_{\mathbf{s}}=\mathbf{62.46}\ \mathbf{emu} /\mathbf{g}, \mathbf{H}_{\mathbf{c}}=\mathbf{2.07}$
KOe, and
$\boldsymbol{M}_{\mathbf{r}}/\boldsymbol{M}_{\mathbf{s}}=\mathbf{0.885}$
. This provides an important reference for the preparation of hexagonal ferrites with high performance.