Ảnh hưởng của việc sấy lên từ tính của vật liệu composite Ba1-XLaxFe₁₂O₁₉/polyaniline

94 Tran Ngo, Tran Nguyen Tien / Tạp chí Khoa học và Công nghệ Đại học Duy Tân 02(45) (2021) 94-102 
 02(45) (2021) 94-102
 Effect of drying on magnetic properties of Ba1-xLaxFe12O19/polyaniline 
 composites 
 Ảnh hưởng của việc sấy lên từ tính của vật liệu composite Ba1-xLaxFe12O19/polyaniline 
 Tran Ngoa,c*, Tran Nguyen Tienb,c 
 Trần Ngọa,c*, Trần Nguyên Tiếnb,c 
 aCenter for Materials Science, Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam 
 aTrung tâm Khoa học Vật liệu, Viện Nghiên cứu và Phát triển Công nghệ Cao, Đại học Duy Tân, Đà Nẵng 
 bCenter for Advanced Chemistry, Institute of Research and Development, Duy Tan University, Da Nang, 550000, 
 Vietnam 
 bTrung tâm Hóa học Tiên tiến, Viện Nghiên cứu và Phát triển Công nghệ Cao, Đại học Duy Tân, Đà Nẵng 
 cFaculty of Natural Sciences, Duy Tan University, Da Nang, 550000, Vietnam 
 cKhoa Khoa học Tự nhiên, Đại học Duy Tân, Đà Nẵng 
 (Ngày nhận bài: 17/03/2021, ngày phản biện xong: 24/03/2021, ngày chấp nhận đăng: 29/03/2021) 
Abstract 
Composites of Ba1-xLaxFe12O19/polyaniline were successfully prepared. By using X-ray diffractometer, the secondary 
phase of α-Fe2O3 was detected besides the main phase of Ba1-xLaxFe12O19. Phase percentage of α-Fe2O3 increased with 
the increase of La doping concentration. Lattice parameters, a and c, of the main phase were decreased with respect to 
the increase of the La doping concentration, x. The decrease of a and c could be attributed to the substitution of small 
 3+ 2+
ionic of La to the larger one of Ba . The effects of drying on magnetic properties of Ba1-xLaxFe12O19/polyaniline 
composites were studied in two cases: un-dried and dried composites. All the magnetic parameters such as saturation 
magnetization, remanent magnetization, coercivity, magnetocrystalline anisotropy, magnetocrystalline anisotropy 
constant, and magnetocrystalline anisotropy field of the dried composites were lower than the undried ones. This 
change would affect the microwave absorbing properties of the composites. 
Keywords: Hexaferrite; polyaniline; composite; magnetic properties. 
Tóm tắt 
Chúng tôi đã chế tạo thành công vật liệu composite của Ba1-xLaxFe12O19/polyaniline và tiến hành khảo sát cấu trúc bằng 
máy tán xạ phổ tia X. Bên cạnh pha chính của Ba1-xLaxFe12O19, phổ tán xạ tia X còn ghi nhận sự xuất hiện của pha phụ 
α-Fe2O3. Tỉ lệ phần trăm của pha phụ α-Fe2O3 tăng khi nồng độ pha tạp La tăng lên. Các thông số mạng a và c của pha 
chính giảm khi nồng độ La tăng lên. Điều này có thể là do sự thay thế của một ion có bán kính nhỏ (La3+) cho một ion 
có bán kính hơn (Ba2+). Ảnh hưởng của việc sấy lên tính chất từ của vật liệu composite cũng đã được khảo sát. Để tiến 
hành khảo sát này, vật liệu composite ban đầu được chia thành hai lô: lô 1 được giữ nguyên sau khi chế tạo (gọi là 
“không sấy”) và lô 2 được đem đi nung ở 170C (gọi là “sấy”). Thông số từ thu được từ hai lô composite thể hiện sự 
khác nhau lớn. Tất cả các giá trị của từ độ bão hòa, từ dư, lực kháng từ, tính dị hướng từ, hằng số dị hướng từ và trường 
*Corresponding Author: Tran Ngo; Center for Materials Science, Institute of Research and Development, Duy Tan 
University, Da Nang 550000, Vietnam; Faculty of Natural Sciences, Duy Tan University, Da Nang, 550000, Vietnam. 
Email: tranngo@duytan.edu.vn 
 Tran Ngo, Tran Nguyen Tien / Tạp chí Khoa học và Công nghệ Đại học Duy Tân 02(45) (2021) 94-102 95 
dị hướng từ của “sấy” composite luôn thấp hơn “không sấy” composite. Sự thay đổi về từ tính này sẽ có ảnh hưởng đến 
tính chất hấp thụ sóng viba của composite. 
Từ khóa: Hexaferrite; polyaniline; composite; tính chất từ. 
1. Introduction second and third approaches by substituting La 
 to Ba site of BaM and composites with PANI, 
 Barium M-type hexaferrite (BaFe12O19, 
BaM) and strontium M-type hexaferrite respectively. 
(SrFe12O19, SrM) belong to the hexaferrite In order to fabricate composites, we firstly 
family which includes six types: M-, W-, Y-, Z, prepared Ba1-xLaxFe12O19 compounds with x = 
U-, and X-types. M-type hexaferrite has 0–0.5. Then, the compounds were carefully 
simplest formula and could be described as mixed with PANI to get the composites. 
BaO/SrO + 6·Fe2O3. BaM is an important hard Finally, we mixed the composites with a binder, 
magnetic material based on its excellent epoxy, to prepare toroidal devices. Magnetic 
characteristics such as: uniaxial loss which comes from magnetic properties of 
magnetocrystalline anisotropy, high composites play an important role to the 
permeability, high saturation magnetization microwave absorption properties. While, the 
(Ms), high coercivity (Hc), and good chemical drying could lead to changes of magnetic 
stability [1]. BaM is also a promising material properties which were motivated us to carry out 
for microwave absorbing due to a magnetic loss this work. In this work, we report the effects of 
which is mainly pr ...  respectively. 
 Table 1. Experimental values obtained from analyzing M(H) hysteresis loops for undried 
composites of Ba1-xLaxFe12O19/polyaniline at room temperature. 
 Sample H M M b H K 
 c r s M /M a 1
 (undried) (kOe) (emu/g) (emu/g) r s (106 Oe2) (kOe) (105 erg/cm3) 
 x = 0 5.06 32.04 58.35 0.55 8.175 11.073 3.231 
 x = 0.1 4.91 32.52 58.86 0.55 8.019 10.967 3.228 
 x = 0.2 5.20 32.61 59.04 0.55 8.096 11.020 3.253 
 x = 0.3 4.52 29.99 54.83 0.55 7.970 10.934 2.998 
 x = 0.4 4.78 28.08 51.78 0.54 8.092 11.017 2.852 
 x = 0.5 5.37 23.72 43.53 0.54 8.293 11.153 2.428 
 In order to compare the Hc tendency of concentration, as shown in Fig. 3. Obviously, 
undried and dried composites, we plotted Hc Hc values of the undried composites higher than 
curves as a function of La-doping that of dried ones for all doping concentration. 
98 Tran Ngo, Tran Nguyen Tien / Tạp chí Khoa học và Công nghệ Đại học Duy Tân 02(45) (2021) 94-102 
In detailed, the Hc values for undried emu/g for x = 0.5. Compared between undoped 
composites decreased for first doping (x = 0.1), and doped composites, drying reduced the Mr 
then increased for x = 0.2, then decreased to values with the reduction in the range of 3–11%. 
lowest value with x = 0.3, and rose up for x = 
0.4 and reached highest value for x = 0.5. The 
case of Hc values for dried composites were a 
bit simple: Hc increased for x = 0.1, then 
decreased for higher doping (x = 0.2–0.4), then 
increased for x = 0.5 composites. The lowest 
and highest values of Hc for dried composites 
were found for x = 0.4 and 0.5, respectively. 
The variation of Hc could be partly attributed to 
the present of α-Fe2O3 and spin canting. 
 In contrary to Hc, tendency of Mr values 
were simple (shown by red curves in Fig. 4). 
 Figure 3. H curves as a function of La-doping 
For undried composites, the Mr slightly c
 concentration for undried (solid-symbol curve) 
increased from 32.04 emu/g for x = 0, to 32.52 and dried (opened-symbol curve) composites of 
emu/g for x = 0.1, to 32.61 emu/g for x = 0.2 Ba1-xLaxFe12O19/polyaniline. 
then decreased for higher doping concentration 
to lowest value as Mr = 23.72 emu/g for x = 0.5. Table 2. Experimental values obtained from 
In the case of dried composites, the Mr analyzing M(H) hysteresis loops for dried 
increased from 30.63 emu/g for x = 0 to 31.47 composites of Ba1-xLaxFe12O19/polyaniline at 
emu/g for x = 0.1, then decreased for higher room temperature. 
doping concentration down to Mr = 21.69 
 Sample H M M b H K 
 c r s M /M a 1
 (dried) (kOe) (emu/g) (emu/g) r s (106 Oe2) (kOe) (105 erg/cm3) 
 x = 0 4.22 30.63 57.13 0.54 8.209 11.097 3.170 
 x = 0.1 4.86 31.47 56.82 0.55 7.955 10.924 3.103 
 x = 0.2 4.64 29.92 54.74 0.55 8.001 10.955 2.999 
 x = 0.3 4.23 28.74 52.45 0.55 7.741 10.775 2.826 
 x = 0.4 3.79 24.91 46.49 0.54 7.980 10.941 2.543 
 x = 0.5 5.03 21.69 39.77 0.55 7.996 10.952 2.178 
 From Fig. 2, we could observe that the where a’ is inhomogeneities (approximately 
hysteresis loops were not saturated in the equal to zero) and b is magnetocrystalline 
applied magnetic field range of 0–10 kOe. anisotropy. The second term of χH is the high-
Therefore, the Ms could be obtained from the field differential susceptibility related to the 
hysteresis loop by employing the “Law of spontaneous magnetization of magnetic 
approach to saturation (LAS)” method. The domains and active in high temperature 
LAS is defined as [27]: analysis. Equation (1) could be shortened to the 
 following equation: 
 , (1) 
 Tran Ngo, Tran Nguyen Tien / Tạp chí Khoa học và Công nghệ Đại học Duy Tân 02(45) (2021) 94-102 99 
 , (2) particles existed in undried and dried 
 composites of Ba1-xLaxFe12O19/polyaniline. 
 In this work, Eq. (2) was used to fit the 
M(H) data at high field of H = 7–10 kOe. The 
values of Ms were plotted in Fig. 4 by black 
curves. For undried composites, Ms slightly 
increased from 58.35 emu/g for x = 0 to 58.86 
emu/g for x = 0.1, to 59.04 emu/g for x = 0.2, 
then decreased for higher doping concentration. 
While, the Ms values of dried composites 
decreased when La concentration increased. 
Similar to Mr values, the Ms values of dried 
composites were lower than undried composites 
with reduction of 2–10 %. The decreasing of Mr Figure 4. Ms and Mr curves as a function of La-doping 
 2+ concentration for undried (solid-symbol curves) 
and Ms was caused by the replacement of Ba and dried (opened-symbol curves) composites of 
 3+
by La , as well as by the presence of the Ba1-xLaxFe12O19/polyaniline. 
secondary phase. Due to the substitution of 
Ba2+ by La3+, the ionic state of Fe reduced from By using LAS, we also determined 
Fe3+ to Fe2+ which might decrease the strength magnetocrystalline anisotropy, b, from the 
of the Fe3+–O–Fe3+ double-exchange slope of fitting line of magnetization where 
interactions. In addition, the weakening of slope is a product of b and Ms. The b values of 
magnetization could be attributed to spin undried and dried composites were shown in 
canting [15, 28]. On the other hand, the the top plot of Fig. 5. The curves of b have 
secondary phase of hematite (α-Fe2O3) is similar tendency to the curves of Hc for undried 
antiferromagnetic which could also be a composites. Compare the b curves between 
contributor to the reduction of Ms and Mr undried and dried composites, the b values of 
values. We also calculated the squareness ratio undried composites were higher than the dried 
Mr/Ms of undried and dried composites (listed ones except x = 0 composite. The K1 values of 
in Table 1 and Table 2). Considering the Mr/Ms undried and dried composites also calculated 
ratio, the following phenomena was through the following expression: 
determined: (i) Mr/Ms < 0.5: there is a 
dominance of the magnetostatic interaction , (3) 
between particles; (ii) Mr/Ms = 0.5: there is a With b and Ms obtained above, we have 
dominance of randomly oriented non- calculated the values of Ha and K1, listed in 
interacting particles under coherent rotation; Table 1 and Table 2. From Eq. (3), we could 
and (iii) 0.5 < Mr/Ms < 1: exchange coupling clearly observe that Ha is directly proportion to 
between particles takes place [29]. In our b. Therefore, the Ha has the variation 
work, Mr/Ms values were in the range of 0.54– tendencies similar to that of b, as shown in the 
0.55, proving the exchange coupling between bottom plot of Fig. 5. 
100 Tran Ngo, Tran Nguyen Tien / Tạp chí Khoa học và Công nghệ Đại học Duy Tân 02(45) (2021) 94-102 
 Figure 5. (top) Magnetocrystalline anisotropy, b, and (bottom) magnetocrystalline anisotropy field, Ha, curves as a 
function of La-doping concentration for undried (solid-symbol curves) and dried (opened-symbol curves) composites of 
 Ba1-xLaxFe12O19/polyaniline. 
 While, the K1 values which calculated Ms, Mr, Hc, b, Ha, and K1 of the dried composites 
through Eq. (3) showed the similar tendencies were smaller than the undried ones. This 
the that of Ms curves, as shown in Fig. 6. phenomenon could be attributed to the changes 
Overall, all the magnetic parameters such as in the density of composites after drying. 
 Figure 6. Magnetocrystalline anisotropy constant, K1, curves as a function of La-doping concentration for undried 
 (solid-symbol curve) and dried (opened-symbol curve) composites of Ba1-xLaxFe12O19/polyaniline. 
4. Conclusion presence of impurity phase of α-Fe2O3. The 
 The undried and dried composites of phase percentage of α-Fe2O3 increased with 
Ba1-xLaxFe12O19/polyaniline were successfully respect to the increase of La doping 
prepared. The structural properties of dried concentration. Magnetic properties of 
composites studied by XRD which showed the Ba1-xLaxFe12O19/polyaniline composites were 
 Tran Ngo, Tran Nguyen Tien / Tạp chí Khoa học và Công nghệ Đại học Duy Tân 02(45) (2021) 94-102 101 
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