Preparation and Magnetic Properties of BaFe12-2xCox-ySnxNiyO19 Particles

J.

Colloque C1, SupplCment au Journal de Physique I11 de mars 1997

Preparation and Magnetic Properties of BaFel,xCo,,SnxNiy0,9

Particles

Department of Materials Science, Tsing Hua University Hsinchu, Taiwan, China

*

Abstract. BaFelp - z.Co.-,Sn,Ni,01 I hexagonal-plated-shaped barium ferrite powders mere prepared by chemical pri- cipitation and subsequent heat treatment to investigate the effects of Ni ion on the magnetic properties of the barium ferrite powders. Experimental results indicates that if the y value in the chemical formula is varied and the x value is maintained constant, i.e. the partial replacement of Co ion by Ni ion, the particle size and

a. of the powders sere reduced; furthermore, the BC value of the powders would be maximized at a certain y value. If the x value is varied and maintained y=O. 5x, the large the addition of (Co,~eNi,lrSn.) ions causes the more of a decrease in the o value, B e value, and curie temperature.

INTRODUCTION

Hexagonal-plated-shaped barium ferri tes are a highly promising material for perpendicular recording media,

if its Hc can be reduced for easier writing by the magnetic head. The HE of barium ferrites can be reduced

by simultaneously adding Co and Sn ions [l] to replace some FeeO3. Since Ni ion is a component of Ni-Zn

soft ferrites, adding Ni ions to replace some Co ions may affect the Hs value of barium ferrites. In this

report, the effects of magnetic properties of barium ferrites are examined by (1) partially replacing Ni

ion for Co ion at a fixed Sn ion, i. e. changing y value and maintaining the x value constant in BaFel 2-zx

C O ~ - ~ S ~ ~ N ~ , O I ~ , and (2) varying the x value and maintaining at y=0.5x. EXPERIMENTAL

Acidic aqueous solutions containing BaCl z -2Hz0, FeCla-GHzO, CoC12-Hz0, SnClr-5Hz0, and NiClz-6Hz0 were pre-

cipitated by adding NazCOa solution. Hexagonal-plated-shaped BaFe~z-z~Co~-,Sn~Ni~O~g particles were ob-

tained by washing, drying, and finally heating the precipates at 600-900°C for various times. RESULTS AND DISCUSSION

XRD analysis in Figure 1 indicates that the major phases of the precipitates after the heat treatment at 650°C is a-FezOo; barium ferrite phase starts forming at 750°C. Electron micrographs in Figure 2 reveal that the particle shape of the ferrite powders is hexagonal-plated. When the ferrite powders are heat treated at 850% for Ihr, the particle size of the ferrite powders ranges between 0.4~. to 0.25~. when the y value (Ni ion content) is between 0.2 to 0.8, while maintaining at x=1.0. Moreover adding Ni ion de- creases the particle size. While maintaining at x=0.8, adding Ni ion to partially replace Co ion, causes

the o value of the powders to decrease with the Ni ion concentration (Figure 3). However, adding Ni ion

maximizes the Hc value of the ferrite powders at y=0.4. Furthermore partially replacing Co ion by Ni ion

does not significantly affect the powders' magnetic properties. If the replacement of Co ion by Ni ion is

maintained at 50%, i. e. the formula is B a F e ~ z - z ~ C o , l ~ N i ~ / z S n ~ O ~ s, the o value and Hc value (Figure 4) de- crease with the x value, i. e. the concentration of (Co, Ni, Sn) ions. In particular the Hc value decrease

more sharply than the o value. Figures 5 and 6 also reveal that the o value and Hc value not only decrease

with the x value, but also decrease with the measuring temperatures. The curie temperature of the ferrite powders are found about 450°C for x=O and 350% for x=0.8.

C1-540

JOURNAL DE PHYSIQUE IV

[l] K.Sueto, H.Sakumoto, A.Suzuki, and M.Sugimoto, "Ferrites," p.964. Proc. 6th International Conf. on

Ferrites, Tokyo, 1992.

A NaCl &, ferrite a-Fez03

(a) T=650°C

Figure 1 X-ray diffraction patterns of powders heat treated at various temperatures

Figure 2 ~lectron. micrographs of powders

at various x values (Ni contents)

0 L I lo

00 0L C8 12 16

X value in BaFe1z-z~Co.-~Sn=Ni~01o

...

Y value in BaFe1z-~=Co=-~Sn=Ni~019

Figure 3 oa and HC values of powders at various y values Figure 4 as and H, values of powders at various x values

T ( " c ) T t ' c )