Topics in Current Chemistry (2020) 378:6
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1.1.3 Magnetoplumbite Ferrites
Magnetoplumbites are synthetic ferrites first prepared at Philips Lab in the 1950s and
they mainly share the general chemical formula M
2+
Fe 12 O 19 , where M
2+
can be Ba
2+
,
Pb
2+
, Sr
2+
or Ca
2+
. Although they are labelled also as hexaferrites, they crystallize in
a hexagonal or rhombohedral symmetry structure. In addition to the MFe 12 O 19 form
(labelled as M-type ferrite, Fig. 2), they can be categorized within five other groups,
consisting in M 1–4 Me 2 Fe 12–36 O 22–60 type ferrites. While M
2+
is considered as a large
divalent cation, Me
2+
represents usually a smaller divalent first-row transition metal
cation such as Co
2+
, Fe
2+
, Zn
2+
or Ni
2+
. They are consequently categorized as Z-type
(Ba 3 Me 2 Fe 24 O 41 ), Y-type (Ba 2 Me 2 Fe 12 O 22 ), X-type (Ba 2 Me 2 Fe 28 O 46 ), W-type ferrites (BaMe 2 Fe 16 O 27 ) and U-type (Ba 4 Me 2 Fe 36 O 60 ) ferrites [7]. The most studied magnetoplumbites are ferrites containing Ba and Co as divalent cations, but a large range
of cation-substituted hexaferrites have been investigated, especially M, W, Z and Y
ferrites containing Sr, Zn, Ni and Mg. Hexaferrites can also form many solid solutions, and partial substitution with trivalent or tetravalent cations can be performed.
The reader can refer to the review by Pullar for in-depth analysis [7].
1.1.4 Orthoferrites
Orthoferrites are ferrites with a general chemical formula MFeO 3 , where M is very
often a rare-earth cation, an alkali metal cation or an alkaline earth metal cation.
They crystallize in a distorted perovskite structure with an orthorhombic symmetry
and an ABO 3 formula unit, in which FeO 6 as a rotary tilted BO 6 element fills the
Fig. 2 Perspective view [8] (left) and polyhedra (right) of the unit cell in the case of the M-ferrite structure (BaFe 12 O 19 ) (Fe blue, Ba green, O red). Reproduced with permission from Ref. [7]. Copyright Elsevier and Wiley
110
Reprinted from the journal
1 3
1.1.3 Magnetoplumbite Ferrites
Magnetoplumbites are synthetic ferrites first prepared at Philips Lab in the 1950s and
they mainly share the general chemical formula M
2+
Fe 12 O 19 , where M
2+
can be Ba
2+
,
Pb
2+
, Sr
2+
or Ca
2+
. Although they are labelled also as hexaferrites, they crystallize in
a hexagonal or rhombohedral symmetry structure. In addition to the MFe 12 O 19 form
(labelled as M-type ferrite, Fig. 2), they can be categorized within five other groups,
consisting in M 1–4 Me 2 Fe 12–36 O 22–60 type ferrites. While M
2+
is considered as a large
divalent cation, Me
2+
represents usually a smaller divalent first-row transition metal
cation such as Co
2+
, Fe
2+
, Zn
2+
or Ni
2+
. They are consequently categorized as Z-type
(Ba 3 Me 2 Fe 24 O 41 ), Y-type (Ba 2 Me 2 Fe 12 O 22 ), X-type (Ba 2 Me 2 Fe 28 O 46 ), W-type ferrites (BaMe 2 Fe 16 O 27 ) and U-type (Ba 4 Me 2 Fe 36 O 60 ) ferrites [7]. The most studied magnetoplumbites are ferrites containing Ba and Co as divalent cations, but a large range
of cation-substituted hexaferrites have been investigated, especially M, W, Z and Y
ferrites containing Sr, Zn, Ni and Mg. Hexaferrites can also form many solid solutions, and partial substitution with trivalent or tetravalent cations can be performed.
The reader can refer to the review by Pullar for in-depth analysis [7].
1.1.4 Orthoferrites
Orthoferrites are ferrites with a general chemical formula MFeO 3 , where M is very
often a rare-earth cation, an alkali metal cation or an alkaline earth metal cation.
They crystallize in a distorted perovskite structure with an orthorhombic symmetry
and an ABO 3 formula unit, in which FeO 6 as a rotary tilted BO 6 element fills the
Fig. 2 Perspective view [8] (left) and polyhedra (right) of the unit cell in the case of the M-ferrite structure (BaFe 12 O 19 ) (Fe blue, Ba green, O red). Reproduced with permission from Ref. [7]. Copyright Elsevier and Wiley
110
Reprinted from the journal