HAL Id: jpa-00216969
https://hal.archives-ouvertes.fr/jpa-00216969
Submitted on 1 Jan 1977HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-entific research documents, whether they are pub-lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
GROWTH AND PROPERTIES OF MANGANESE
ZINC TIN FERRITE SINGLE CRYSTALS
H. Watanabe, S. Takeda
To cite this version:
de Mn-Zn-Sn sont les seuls qui présentent un phénomène de précipitation d'une fine phase non magnétique de SnO 2 exempte de toute craquelure. De plus des études cristallographiques et magné-tiques ont été effectuése sur des monocristaux de ferrite de Mn-Zn-Sn avant et après recuit. Les variations de la composition de ces monocristaux présentent des propriétés caractéristiques. Les ions Sn4+ et Fe2+ produits par la substitution de 2 Fe3+ occupent des sites B du réseau spinelle. Par
un recuit sous oxygène, la fine phase SnO 2 précipite dans le plan (111) de la structure spinelle. Toute-fois, même en présence d'une phase SnO 2, on peut obtenir uniquement en ajustant les conditions de recuit, les hautes valeurs de perméabilité nécessaires dans les applications de ces matériaux aux têtes magnétiques.
Abstract. — Studies of the crystal growth and the precipitation of the non-magnetic phase were
made on the Mn-Zn ferrite containing various elements. Mn-Zn-Sn ferrite crystals are the only ones showing the precipitation phenomenon of the fine non-magnetic phase of SnO 2 without any cracks. Furthermore crystallographic and magnetic studies have been made on the Mn-Zn-Sn ferrite single crystals before and after the annealing treatments. The variations of the composition of Mn-Zn-Sn ferrite single crystals show characteristic properties. Sn4+ and Fe2 + ions caused by the
substitution of 2 Fe3+ ions occupy the B lattice point of the spinel structure. By the annealing
treat-ment under the conditions of oxygen atmosphere, fine SnO2 phase precipitate in (111) plane of spinel structure. But even the SnO 2 phase included, high fi property — which is necessary in order to apply for the magnetic head material — can be attained just by the adjustment of the annealing conditions.
1. Introduction. — Generally Mn-Zn ferrite single crystal head, in spite of excellent property of high wear resistance, has not been used for the head of an audio tape recorder because of generation of much noise, that is ferrite head noise, when the tape is running. On the other hand, a head of a poly-crystal ferrite, whith grain size diameter less than 40 um, shows low noise property [1], but inferior wear property.
In previous papers [2], it was reported by authors that a magnetic head made from an Mn-Zn-Sn ferrite crystal, in which much fine texture S n 02
precipita-tions were included, showed low noise property and also high wear resistance. And low noise property of the head was explained as resulting from a change of the magnetization mechanism, that is pinning effect of domain walls, caused by the barrier of fine and ordered S n 02 precipitations.
In this paper, experiments to grow crystals of Mn-Zn ferrite containing various elements and to produce the ordered and fine precipitation of non-magnetic phase like the Sn02 phase are first described. Next,
crystal growth, magnetic properties and precipitation mechanism of S n 02 phase of the Mn-Zn-Sn ferrite
crystals which are the only ones showing the preci-pitation phenomenon of fine non-magnetic phase are
described. Finally, the most suitable conditions for the production of Mn-Zn-Sn ferrite crystals used for a magnetic head that must have a high p. property even with the S n 03 inclusions are described.
2. Crystal growth of Mn-Zn ferrite containing
various elements. — Experiments to grow crystals of
Mn-Zn ferrite with the composition of 53 mol % of F e203, 25 mol % of MnO and 22 mol % of ZnO and
additive elements of various kinds less than 5 mol %, Ca, Y, Ti, Zr, V, B, In, Si, Ge, Sn and Bi were made by the Bridgman method. Table I shows the results of study of the shape, size and location of precipitations and the accompanied cracks in the texture of grown crystals. Some examples of crystals containing the Y, V and Si elements are shown in figure 1. In the texture of most of the crystals, various types of inclusions were observed with non-uniform distribution of shape, size and location. Furthermore, unluckily, inclusions were mostly accompanied with much cracks. However, in the Mn-Zn ferrite crystal containing the Sn element, that is Mn-Zn-Sn ferrite crystal, characteristic pheno-menon was observed. The fine S n 02 phase, of needle
like shape could precipitate remarkably by the anneal-ing treatment under conditions of oxygen atmosphere. That is to say, the Mn-Zn-Sn ferrite crystal was the
6
C1-52 H. WATANABE AND S. TAKEDA
FIG. 1.
-
Photograph of the texture of Mn-Zn single crystal ferrites containing Y. V and Si elements. (X 100) Various types of inclusions (gray parts) are observed and accompanied with many cracks (black parts).Observing results of the texture of Mn-Zn crystal ferrites containing various additive elements Additive Elements Ca Y Ti Zr V B In Si Ge Sn Bi
Precipitation of
Other Phase 0
0
A little0
0 0 A little0
0
A little0
Precipitation0
Shape and Size of
Other Phase A A ~ A A A A A Q O A Uniform 0
Non-uniform A
Crack x x O x x x O x x O x Crack free 0
Crack x
Compositions of Mn-Zn ferrite : FezO, 53 mol
%,
MnO 25 rnol%,
ZnO 22 mol%.
Quantities of additive elements : Less than 5 mol
%.
Crystal growth : By the Bridgman method in 0, atmosphere.
only one crystal which could produce the fine and order- ed precipitation in its own texture.
3. Crystal growth of Mn-Zn-Sn ferrite [3]. -
Mn-Zn-Sn ferrite crystals were grown by the Bridgman method in oxygen atmosphere at about 1660 O C . Compositions of starting materials of these crystals are shown in table 11. Variations of compositions of
TABLE I1
Compositions of raw materials of Mn-Zn-Sn sihgle crystal ferrites Compositions
Sample No. Fe203 MnO ZnO SnO,
No. 1
. . . .
.
. .
49.11 27.33 23.56-
-
No. 2
.
.
.
. .
. .
47.42 26.38 22.75 3.44 No. 3.
.
.
. . .
.
46.61 25.94 22.37 5.08FIG. 2. - Variations of compositions of Mn-Zn and Mn-Zn-Sn
No. 4
. .
. . . .
-
45.84 25.5O 22.00 6.66 single crystal ferrites. Direction of arrow coincides with grownN ~ . 5
.
.
. . .
.
.
44.36 24-69 21.282;
9.67 direction of the single crystal. Solid lines : Mn-Zn-Sn single crystal ferrites. No 1,2, 3 , 4 and 5 correspond to compositions in4. Properties of Mn-Zn-Sn ferrite. - After the analysis of compositions of above-mentioned crystals, changes of lattice constant and saturation flux density B,, of Mn-Zn-Sn ferrite for Sn quantities were measur- ed. Figure 3 shows the property of lattice constant
Temperature ( K)
FIG. 4. -Temperature dependence of saturation flux density Bzo of Mn-Zn-Sn single crystal ferrites. No. 1, 2, 3, 4 and 5 correspond to compositions of Mn-Zn-Sn ferrites in Table 11.
FIG. 3. - Variation of lattice constant of Mn-Zn-Sn single crystal ferrites versus quantities of Sn component.
versus Sn quantity. Lattice constant increases linearly with to Sn content. Figure 4 shows the property of saturation flux density B,, versus temperature, rang- ing from liq. N, to Curie temperature T,. Saturation flux density B,, and Curie temperature T, decrease
respectively in proportion as Sn content increases. These phenomena are explained by the understanding that Sn4' and Fez+ ions are substituted for 2 Fe3+ ions, that is
and occupy the B lattice point of the spinel structure, so that the magnetic interaction between A and B lattice points becomes weak.
5. Precipitation of SnO, [3]. - By the annealing
treatment under proper conditions of oxygen concen- tration and temperature in the neighborhood of 1 200 OC, weight changes result from oxidation or
C1-54 H. WATANABE AND S. TAKEDA
1 : (100) Plane 2 : (1 10) Plane 3 : (1 1 1) Plane
FIG. 6.
-
Diagrams showing the relation between SnO2 directions and crystal planes. Axial directions of SnOz coincide with the intersections of (1 11) planes of spinel structure and the observing plane.reduction of Mn-Zn-Sn single crystal ferrites and accordingly SnO, phase easily precipitates from or disappears into the texture of single crystal ferrite. Figure 5 shows the SnO, phase precipitating in observ- ing planes of (loo), (110) or (111) of Mn-Zn-Sn single crystal ferrite respectively. Axial directions of precipitation coincide with the intersections of (1 11) planes of spinel structure and the observing plane (Fig. 6). It becomes evident that the SnO, phase precipitate only in (111) plane of the spinel structure.
FIG. 7. - Diagram showing the relation between SnOz preci- pitation and the annealing temperature and oxygen atmosphere in Mn-Zn-Sn ferrite system. Number shows the rate of increase in the weight of Mn-Zn-Sn ferrite by oxidation. Standard compo-
sitions : Fe203 49.11 mol % ; MnO 27.33 ; ZnO 23.56.
Figure 7 shows the phase diagram of SnO, precipita- tion under conditions of the annealing temperature and oxygen atmosphere in Mn-Zn-Sn ferrite system. Solid line shows the limit line of SnO, precipitation and dotted line shows the line of a-Fe203 precipitation. In this figure, for example, as oxygen partial pressure increases at 1 200 OC, SnO, phase begins to precipitate just at the solid line and after that its quantity gradually increases. Furthermore a-Fe203 phase also starts to appear.
6. Magnetic properties of Mn-Zn-Sn ferrite contain- ing SnO, phase. - Table 111 shows some examples of magnetic properties of Mn-Zn-Sn ferrite crystals containing SnO, phase. Magnetic properties strictly change by the conditions of the annealing treatment and precipitation density of the SnO, phase. Generally, as SnO, increases, coercive force Hc becomes larger and permeability p smaller. But even if SnO, phase is included, high p property can be obtained by the adjustment of annealing conditions. For example, as shown in table 3, by the conditions of the 2nd annealing treatment after the 1st one, permeability p can be varied without any change of SnO, precipita- tion. The reason for this phenomenon is thought to be the same as the reason for the permeability p of poly-crystal ferrite because various values can be attained just by the adjustment of the annealing conditions of temperature and oxygen partial pressure without changing the grain size diameter.
2nd cycle Photo 2 1 120 OC 0.12
%
0, 5 110 3 100 0.03 111OoC1 % 0 2 1 030 2 650 0.23 2nd cycle As shown in 1 120 OC 0.12%
0, Photo 3 2 570 2nd cycle 1 120 OC 0.06%
0, 3 810Photo 1 Photo 2 Photo 3 ( x 400)
shows the low noise property being equal to that of 3. Annealing conditions
permalloy head. But it is also desirable that the material 1st cycle : Temperature : 1 110 OC
for a magnetic head shows higher ,u property for Atmosphere : 1
%
0, (Balance N,) obtaining higher out-put. Then one of the most Times : 4 Hsuitable conditions for the production of Mn-Zn-Sn 2nd cycle : Temperature : 1 120 OC
ferrite crystals, used for the magnetic head material of Atmosphere : 0.06
%
0 , (Balance N,)an audio tape recorder, is described as follows. Times : 4 H 1 . Compositions Fe,O, ; 47.4 mol
%
4. ResultsMnO : 26.4 SnO, density : As shown in Photo. 3.
ZnO : 22.8 Magnetic properties :
SnO, : 3.4 Permeability p at 1 kHz :
-
3 810 Saturation Flux Density B,, :-
3 100 G 2. Crystal growth : By the Bridgman method Coercive Force Hc :-
0.08 Oe.Oxygen atmosphere Noise property of a head : Same as permalloy
About 1 660 OC head.
References
[I] WATANABE, H. and YAMAGA, I., Japan. J. Appl. Phys. 10
(1971) 1741.
[2] WATANABE, H. and YAMAGA, I., IEEE Trans. MAG-8 ( 1 972) 497 ;
