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The Static and Hyper-frequency Magnetic
Properties of a Ferromagnetic-Ferroelectric
Composite
Yang Bai
1
, Fang Xu
1
, Lijie Qiao
1
, Ji Zhou
2
and Longtu Li
2
1.Corrosion and Protection Center, Key Laboratory of Environmental Fracture (Ministry of
Education), University of Science and Technology Beijing, Beijing (100083)
2.State Key Laboratory of New Ceramics and Fine Processing,
Department of Materials Science and Engineering, Tsinghua University, Beijing (100084)
E-mail: baiy@mail.ustb.edu.cn ,lqiao@ustb.edu.cn
Abstract
This paper reports the static and hyper-frequency magnetic properties, as well as their relationship
with microstructure, of the ferromagnetic-ferroelectric co-fired composite ceramic, consisting of
Y-type hexagonal ferrite and perovskite-type ferroelectric. X-ray diffraction results did not detect
any other phase in the co-fired ceramics, but found a crystal structural distortion of hexagonal
ferrite. Scanning electron microscopy photos showed that two phases’ grains matched well and
stacked compactly, and hexagonal ferrite changed its grain morphology. The saturation
magnetization increased with the reduction of magnetic phase in the range of 0<x<0.3 because of
the stress induced structural distortion. Permeability decreases monotonically with the reduction of
magnetic phase in the whole composition range.
Keywords: Co-firing, Composites, Ferrites, Microstructure, Magnetic properties
1 Introduction
In recent years, ferromagnetic-ferroelectric composite is one of the most attractive
subjects in terms of materials science. Many new properties induced by the coupling between
ferromagnetic phase and ferroelectric phase, such as magnetoelectric effect and
magnetooptical effect,
[1-4]
have been arousing much attention. Their multifunctionality is also
greatly needed in the novel integrated components, with the rapid development of portable
electronic products and wireless technology.
[5-7]
Hence, many material systems, such as
BaTiO
3
+NiCuZn ferrite, Pb(ZrTi)O
3
+NiCuZn ferrite, and Bi
2
(Zn
1/3
Nb
2/3
)
2
O
7
+NiCuZn ferrite,
have been prepared, and exhibit fine dielectric and magnetic properties.
[7-14]
It is better to achieve both large magnetization and polarization for multiferroic materials.
But it is hard to reach due to the dilution effect in ferromagnetic- ferroelectric composites. The
properties of composites are not only dominated by that of each phase, but also affected by the
co-firing behavior and microstructure. Then it is possible to enhance magnetization or
polarization inverse to the dilution effect by controlling the microstructure. In this paper, we
focus on the relationship of co-firing behavior and microstructure with the magnetic properties
of the co-fired composite ceramics, Ba
2
Zn
1.2
Cu
0.8
Fe
12
O
22
(BZCF) /
0.8Pb(Ni
1/3
Nb
2/3
)O
3
-0.2PbTiO
3
(PNNT). The saturation magnetization is found enhance with
the reduction of magnetic phase, which is controlled by the microstructure. This work suggests
that it is feasible to enhance magnetization and polarization simultaneously in a multiferroic
composite by modulating the microstructure.
2 Experimental
In this experiment, BZCF / PNNT composite ceramics were prepared by standard
ceramics method. PNNT was fabricated via a columbite-type route, using analytical reagent
grade (AR) PbO, NiO, Nb
2
O
5
and TiO
2
(Beijing Chemical Works, China) as raw materials. The
precursor of NiNb
2
O
6
was formed at 1000
o
C for 3 hours, and then mixed with PbO and TiO
2