Magnetic properties of materials in the CaOP2O5Fe2O3 systemBinod Kumar and Christina H. Chen Citation: Journal of Applied Physics 75, 6760 (1994); doi: 10.1063/1.356845 View online: http://dx.doi.org/10.1063/1.356845 View Table of Contents: http://scitation.aip.org/content/aip/journal/jap/75/10?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Comparison of magnetic and thermoelectric properties of (Nd,Ca)BaCo2O5.5 and (Nd,Ca)CoO3 J. Appl. Phys. 111, 07D727 (2012); 10.1063/1.3679561 Structural and magnetic properties of Co ∕ α Al 2 O 3 ∕ Fe magnetic tunneling junction system: Ab initioinvestigations J. Appl. Phys. 99, 08T302 (2006); 10.1063/1.2150802 Temperature dependent magnetic properties of the 1.2μm bubble diameter compositions(La,Sm,Lu,Tm)3(Fe,Ga)5O1 2 and (La,Sm,Lu,Tm,Ca)3(Fe,Ge)5O1 2 J. Appl. Phys. 55, 2545 (1984); 10.1063/1.333723 Spin Orientation and Magnetic Properties of Ca2FeAlO5 J. Appl. Phys. 39, 1122 (1968); 10.1063/1.1656192 Magnetic Properties of Substituted Ca2Fe2O5 J. Appl. Phys. 38, 1455 (1967); 10.1063/1.1709664

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Magnetic properties of materials in the CaO-P,O,-Fe,O, system Binod Kumar and Christina H. Chen University of Duyton Research Institute, Dayton, Ohio 45469-0170

The magnetic properties of numerous compositions in the ternary CaO-P,O,-Fe,O, system have been studied. A relatively wide glass formation region is located around the PZ05 corner of the system. The Fe,03-containing glasses exhibit paramagnetic behavior. The specimens inside the composition range Fe,0+=30% consist of both paramagnetic and ferrimdgnetic phases.

Glass formation in the CaO-P20,-Fe,O, system has been known and studied for over two decades.‘-” The system pro- vides a wide range of glass specimens for optical and mag- netic studies. Iiowever, the motivation for early studies was primarily academic. The phosphate glass-forming system has recently attracted considerable attention biomaterials.“-7

as potential The CaO-P,O -Fe,O, ” 5 system has also been

of considerable interest in steel making.’ In C!aO-P,05-Fe,O, glasses and slags, iron exists in pri-

marily two oxidation state.s, the Fe’+ and Fe”’ states, which give rise to well documented characteristic optical and mag- netic phenomena. The magne.tic susceptibility of a few com- positions in the CaO-P,05-Fez03 system has been measured and reported by Sanad et uZ..~ However, a complete under- standing of the basic mechanisms leading to variations in magnetic properties in a wide range of compositions is lack- ing. Thus, the purpose of this study is to conduct a limited but systematic study of the magnetic properties in the CaO-P,O,-FezO, system.

The compositions used in this investigation are shown in Table I. The details for sample preparation were reported earlier.’ After casting, the materials were annealed at SO0 “C in air. ?ivo were fnrther heat treated before being character- ized for magnetic properties. Magnetic susceptibility was measured using a Princeton Vibrating Sample Magnetometer Model 151 from 20 to 500 “C. A few specimens were also characterized for microstructures using optical microscopy, SEM, and energy dispersive x-ray anaIysis.

Figure 1, a ternary diagram, shows the locations of the synthesized compositions. General observations on these compositions are presented in Table I. Based on these obser- vations and magnetic measurements, the CaO-P,O,-Fez03 system is divided into three regions: glass-forming region, refractory region (T,>1400 “C)? and ferrimagnetic region.

The glass-forming region has a relatively wide composi- tion range around the P20s corner. In this region, specimens were melted easily in the temperature range of ‘LOOO- 1400 “C and retained their vitreous character during the cast- ing and heat treatment processes. Some compositions inside the ferrimagnetic region also melted with relative ease; how- ever, they crystallized during the casting and heat treatment processes. Compositions with (CaO+Fe,O,jXO% exhibited significant refractoriness, and three (Nos. 8, 11, and 12) did not melt.

Figure 2 shows magnetic susceptibility, x, as a function of temperature for three specimens: Nos. 17, 18, and 19. These compositions are located in the glass-forming region. The calcium phosphate glass, No. 19, alone exhibits diamag-

netic behavior with a negative x, which is relatively indepen- dent of temperature. When iron is introduced to the binary phosphate glass, it gives rise to paramagnetic behavior, the degree of which is directly related to the iron concentration. Pammagnetism originates from the presence of permanent magnetic dipole moments in the materials. Both oxidation states of iron, Fe’+ and Fe3+, lead to permanent dipole mo- ments. The magnetic moment of Fe” ‘, with five unpaired electrons, is higher than that of F’+, which has only four. It has recently been reported that the melting atmosphere has a major influence on the relative proportion of Fe” and Fe”’ states in these glasses.‘” In general, the oxidizing atmosphere increases the proportion of Fe”‘. The melting atmosphere- induced redox state also affects the resulting physical and chemical properties of the glasses.7 The paramagnetism of Nos. 17 and 18 exhibit significant temperature dependence. Specimen No. 17 is a weaker paramagnetic material whose magnetic susceptibility is close to zero at elevated tempera- ture. In general, paramagnetic susceptibility decreases with increasing temperature.

Paramagnetic materials show a linear relationship be- tween applied magnetic field, H, and specific magnetization, LT. Ferrimagnetism yields a nonlinear relationship between Ii and CT and also results in a hysteresis effect. The bulk speci- mens 5, 6, 7, 9, and 10 located in the ferrimagnetic region

TABLE I. Compositions and observations in the CaO-PLOS-FeQ3 system.

Cumposition (wt %)

CaO P,O, Fe,O, Observations

1 10 2 20 3 30

4 40 5 10 6 20 7 30

8 40 40 20 Y 10 30 60

III 20 30 50

11 30 12 40 13-16 4-W 17 16 18 11 19 28

50 40 50 30 so 20

5u 10 40 SO 41) 40 40 30

30 40 30 30

65-70 20-30 79 5 79 10 72 0

Good glass Glass with a crystallized surface Melted but could not be poured out

of crucible Very little formation of liquid phase Good liquid but crystallizsd during cast Good liquid but crystallized during cast Melted but could not be poured out

of crucible Did not melt Good liquid but crystallized during cast Melted but could not be poured out

of crucible Incomplete melting Did not melt Good glass Good glass tiood glass Good glass

6760 J, Appl, Phys. 75 (IO), 15 May 1994 0021-8979/94/75(10)/6760/3/$6.00 Q 1994 American Institute of Physics

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Fe303

A Femmqnetlc Rcgmn

Glare Fomlation

FIG. I. Synthesized composit ions in the CaO-P205-F& systt‘m.

contain both paramagnetic and ferrimagnetic phases. Mag- netic properties of these bulk specimens are comprised of contributions from both phases. Figure 3(a) shows a (r vs H plot of bulk No. 6 heat treated at 700 “0. The bulk magnetic response is resolved into ferrimagnetic and paramagnetic contributions as shown in Figs. 3(‘b:) and 3(cj.

Magnetic parameters n&C, IT~~, rrr, and x of specimens 2, 5, 6, 7, 9, and 10 are presented in Table II. It is interesting that the paramagnetic contributions remain constant at --6X10-” emu/(g Oej for all the specimens in the ferrimag- netic region. The paramagnetic phase is believed to be a vitreous phase containing Fe-703, whereas the ferrimagnetic phase is a crystalline phase containing mostly P20s and kLJ Specimen 10 ~20~3~O~4(:lP,0~~50Fe20,) has the high- - 3. est saturation rr,;--26.0 emu/g. Optical microscopy of speci- men I.0 revealed three phases. The volume fraction of the ferrimagnctic phase as determined from optical microscopy is about 83%. From this data, the ~r,~ for a single ferrimag- netic phase is estimated to be 31 emu/g which is higher than that for cubic ferrites hqg0.Fe203 and Cu0.Fe,03.

20

z ci .fg 2 10

,u’ E f 5 s LE P B 0 24 rz

-10

. . xm(totarsp,,

. . #,7!5% hZUl)

. * “19 (Cd -PhxGlasrl .

. . .

. ..sm .

A. . *A.. . . . m....

A* =m. .A’&...

AA A’A*AA..*

*,t*,,*+,t*,*~***‘~*‘+*~*

II, 1, I, 1 , 1

0 100 200 300 400 500 600

Temperature (‘C)

FIG. 3. Magnetic susceptibility ,k vn temperature of Nos. 17, 18, and 19.

J. Appt. Phys., Vol. 75, No. 10, 15 May 1994

G z c b 2

0 I I I -I 0 4000 8000 12000 18000

Magnetic Field(Oe)

FIG. 3. Magnetization curve of No. 6 heat treated at 701) “C. (a) Bulk, 0) ferrimagnetic phase, (c) paramagnetic phase.

The magnetization curves of No. 5 are shown in Fig. 4. After annealing at 500 “C, No. 5 displays ferrimagnetic be- havior with a large hysteresis loop: remanent magnetization 8,=29.5 G (0,=0.3 emu/gj and intrinsic coercivity ,H, =450 Oe. The specimen was further heat treated at 600, 700, 750, and 850 “C for 24 h. The higher the heat treatment temperature, the lower the degree of ferrimagnetism, and it vanishes at 850 “C. Specimen No. 6 exhibited similar behav- ior. Table III presents a comparison of the magnetic proper- ties of Nos. 5 and 6 for similar heat treatments. It is apparent that No. 6 p0ssesse.s ferrimagnetism superior to that of No. 5, in spite of the fact that No. 6 has a lower iron concentration. However, additional heat treatments have a negative effe.ct on the ferrimagnetic behavior of both specimens.

In an attempt to characterize the ferrimagnetic phase, specimen No. 5 was examined using scanning electron mi- croscopy and energy dispersive x-ray analysis. The scanning electron micrographs for the 500 “C annealed and 850 “(3 heat-treated specimens are shown in Fig. 5. The microstruc- tures of the specimens consist of three phases: dark gray, gray, and light gray. For the specimen after 850 “C/24 h heat treatment, its dark-gray and light-gray phases increase from 26% and 15% to 36% and 42%, respectively, and its gray

TABIE II. Ferrimagnetic pammagnetic properties of the composit ions in the ferrimagnctic region at room tempcrature.a

Ferrimagnetism of hulk specimen Paramagnetism

Sample LUH‘ cr, w, Ferrimagnetic ,y=M/H NO. iOe) (emu/g) (emtig) phase (emu/g Oe)

2 . . . . . . . . . 0% 5.0 x 10-S 5 450 1.5 Il.3 1.2 x 10-5 6 325 ?..l 0.7 6.2 x 1oF 7 125 5.9 0.9 5.8 x lo-” 9 -80 -0.01 CO.01 6.2 x 10-5

10 110 26.0 3.1 83% 6.7 x lo.-”

“All the specimens were heat treated at 500 “C but No. 6 was heat treated at 700 T.

B. Kumar and C. H. Chen 6761 [This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP:

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2

!

~_lll............................~. --- -.. SOOw2

p I-’ ‘i L D 2 i 1 .- 0’

i

8

‘G zi v) -1

i

i

-2 -+..~~“~ I- i 7--- r ----r -4000 -2000 0 2000 4000

W’ef

FIG. 4. Magnetization vs magnetic field of No. 5 as a function of heat treatment temperatures.

phase diminishes from 59% to 22%. Thus, we believe that this gray phase is responsible for the observed ferrimag- netism. The energy dispersive analysis reveals a composition of this phase to be approximately 3Fe,03eP,0s.

The lack of phase e.quilibrium and crys%ographic data in the. CaO-P&-Fe20, system has limited our ability to ana- lyze and identify the ferrimagnetic phase in the system. However, it is interesting to note that a ferrimagnetic com- pound exists in the CaO-P,O,-Fe,O, system. The phosphate- based magnetic materials may potentially have some appli- cation in the field of biomedical engineering.

Three regions have been found in the CaO-P20sFe,03 system. A wide glass-forming region is located around the P,O, corner, in which bulk specimens could be prepared us- ing a normal casting procedure and cooling rate. The calcium phosphate glass exhibits temperature independent diamagne-

TABLE III. Comparison of magnetic properties of Nos. 5 and 6.

700 “C/24 h 750 “Cl24 h 850 Vi’24 h Sample

No. B,(G) .dfJW B,(G) yffc(Oe) B,(G) &WC)

5 14.3 450 7.5 450 0 0 6 2x.9 32.5 8.4 370 0.9 300

6762 J. Appl. Phys., Vol. 75, No. 10, 15 May 1994

03

FIG. 5. Microstructures of No. 5 ilOCaO~4~~P,O,~SOFe,O~, wt %). (aj After 500 “C annealing, fbj after 850 “C/24 h heat treatment.

tism. Adding iron to the calcium phosphate system leads to paramagnetic behavior. A ferrimagnetic region is located in the composition range with 10%30% CaO, 30%40% PIOs, and 230% Fe?O,. Samples inside the region contain both paramagnetic and ferrimagnetic phases. Subsequent heat treatments at 600--850 *C reduces or destroys the ferri- magnetism.

‘A. Bishay and k Kinawi, Proceedings of the International Congress, Physics of Non-Crysfuflirte Soli&, Delft, Netherlands, July 1964 (North- Holland, New York, l%sj, p. 589.

‘C. Hirayama, J. G. Castle, Jr., and M. Kuriyamd, Phys. Chem. Glasses 9, 109 !19fl8).

3R. J. Edwards, A. Paul, and R. W. Douglas, Phys. Chcm. Glasses 13, 137 (19723.

“B. Kumar, C. H. Chen, Phys. Chem. Glasses (to be publishedj ‘B. Kumar, Trans. Indian Gram. Sot. 44, 123 tl985j. ‘G. Graves and B. Kumar, IJ. S. Patent No. 4,dtl4,097, 5 August 19%. 7B. Kumar and S. Lm, J. Am Gram. Sot. 74, 226 (1991j. *A. Muan and E. F. Osbom, Phase ~quifibria Among 0Cde.r in SteeL Mak-

ing (Addison-Wesley, Reading, MA, 1965), pp. I%- 165. ‘A. M. Grad, I. Kashif, M. A. Khaled, S. A. Aly, and H. Farouk, Phys.

Chem. Glasses 30, 27 (1989). t”B. Kumar, C. H. Chen, and S, Lin. Phys. Chem. Gkdsses 33, 45 (1992).

B. Kumar and C. H. Chen

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