Extraordinary magnetic properties of lafeo3 system doped ti, co, cu - Nguyen Thi Thuy

Journal of Science and Education, College of Education, Hue University ISSN 1859-1612, No. 03(43)/2017: pp. 32-38 Received: 23/5/2017; Revised: 30/6/2017; Accepted: 07/7/2017 EXTRAORDINARY MAGNETIC PROPERTIES OF LaFeO3 SYSTEM DOPED Ti, Co, Cu NGUYEN THI THUY - TRAN DUY THANH CAO THỊ THUY LINH - HOANG HUONG QUYNH Physics Department, Hue University of Education, Hue University Email: nguyenthithuy0206@gmail.com Abstract: LaFeO3 system with doped Ti, Co, Cu was manufactured by solid state reaction method, it was sintered at 12500C and 12900C in 10 hours with a heating rate of 30C/min. Using X-ray diffraction and Scanning Electron Microscope (SEM) to examine the structure, it reveals that samples are single-phase and orthogonal-perovskite structure describing by the Pnma space group, the unit cell volume of the samples increases when Ti, Co, Cu are doped to replace ion Fe+3. The size of particle increase while raising the temperature of sintering. Doping Ti, Co, Cu ions has strongly changed the magnetic properties of the sample system. Magnetic hysteresis loops M(H) and magnetocaloric M(T) of the samples are measured in different magnetic fields and show interesting results. All the samples shown strong ferromagnetism, among which La(Fe0.4Cu0.1Ti0.5)O3 shown the strongest and its Curie temperature is about 4500C. Keywords: LaFeO3 doped Ti, Co, Cu; magnetic hysteresis loop M(H); magnetocaloric loop M(T); strong ferromagnetism 1. INTRODUCTION Perovskite material has the general form ABO3 with A is the cation of rare earth element or alkaline earth metals (Y, La, Nd, Sm, Ca, Ba....), B is the cation of transition metal (Mn, Co, Fe). The replacement of different elements into position of A or B or simultaneously replacing two positions can create lots of change in nature. When there is a doping, the electric property of perovskite materials has a lot of promising improvements to suit different application purposes. Studies on the manufacture and investigating perovskite materials have been made with familiar families of materials such as SrTiO3, LaMnO3, CaMnO3, LaFeO3 [1-8]. When part of the ion of Ln (rare earth element), Mn or Co is replaced by ions of lower or higher valence, there exist a valence mixture state (Mn3+/Mn4+, Co3+/Co4+ or Fe3+/Fe4+). The structure is distorted, which leads to the appearance of some special magnetic properties or some important magnetic effects namely, Giant Magneto Resistance – GMR, Collosal Magneto Caloric Effect – CMCE. These promise to bring many applications in electronics, information, radio telecommunication, magnetic cooling which does not pollute the environment. 2. MATERIALS AND METHODS The sample LaFeO3 doped Ti, Co, Cu is manufactured by solid state reaction method, oxides La2O3(99.5%), Fe2O3(99%), Co2O3(99%), TiO2(99%), CuO(99%) are blended EXTRAORDINARY MAGNETIC PROPERTIES OF LaFeO3 SYSTEM DOPED Ti, Co, Cu 33 followed the nominal component, mixture was crushed and mixed once in 12 hours with distilled water then compressed into cylindrical pellets ( 10 , 10mm h mm  ) and conducted preliminary calcination at 900oC in air for 8 hours. During the calcinating process, the reaction between the ingredients in batches, occur at high temperatures to form solid solution. After preliminary calcination, samples were crushed in dry and wet way for 5 hours. After the material was crushed the second time, it was well mixed with 2% of binder which is PVA solution. Next the sample was pressed into the block which has size 12 4 3mm mm mm  and put into sintered at 1290 oC for 10 hours with a heating rate of 3oC/min. The sample, then, is cooled under the oven. The structure was investigated by using X-ray diffraction via diffractometer D5005 which uses Kα radiation of the copper element and the diffraction angle 2θ varied from 10 to 70o with each step of 0.02o. The M(H) and M(T) loop are measured in the magnetic field from 2 Tesla in room temperature up to 9000C on the MicroSense Easy VSM Software version 20130321-02 of the Institute of Advanced Science and Technology (AIST), Polytechnic University of Hanoi. 3. RESULTS AND DISCUSSIONS X-ray diffraction patterns of LaFeO3 system doping Ti, Co, Cu are presented in Figure 1 and Figure 2. The clear sharp peaks are assigned to be single-phase of the orthogonal- perovskite structure describing by the Pnma space group. According to the results of X-ray diffraction, lattice parameters and unit cell volume of the samples are calculated and presented in Table 1 and Table 2. It can be seen from the data that the unit cell volume of samples increases while replacing ion Fe+3 by ion Ti+4, Co+3, Cu+2. The reason is that the radius of ion Ti+4 (r = 0,650 Å), Co+3 (r = 0,648 Å) and Cu+2 (0,730 Å) is larger than the radius of ion Fe+3 (r = 0,645 Å). The crystal lattice deformation when doping Ti+4, Co+3, Cu+2 into LaFeO3 is the main reason affecting the magnetic properties of samples. Table 1. Lattice parameters, unit cell volume of sintered samples at 12900C 10 20 30 40 50 60 70  (®é) C - ê n g ® é ( ® .v .t .y ) (5) (4) (3) (2) (1) 242240202220 121 101 Fig. 1. X-ray diffraction diagram of samples sintered at 12900C: LaFeO3 (1), La(Fe0,6Ti0,4)O3 (2) , La(Fe0,5Ti0,5)O3 (3), La(Fe0,4Co0,1Ti0,5)O3 (4) and La(Fe0,3Co0,2Ti0,5)O3 (5) 10 20 30 40 50 60 70  (®é) C - ê n g ® é ( ® .v .t .y ) 242141 240202 220 121 101 (2) (1) Fig. 2. X-ray diffraction diagram of La(Fe0,4Cu0,1Ti0,5)O3 sintered at 12300C (1) and 12500C(2) 34 NGUYEN THI THUY et al. Table 1. Lattice parameters, unit cell volume of sintered samples at 12900C Table 2. Lattice parameters, unit cell volume of La(Fe0,4Cu0,1Ti0,5)O3, sintered at 12300C and 12500C Figure 3 is SEM images of Ti and Co doped samples, sintered at 12900C. The size of the particles is quite homogeneous. Figure 4 is SEM images of Ti and Cu doped samples, sintered at 12300C and 12500C. In the sample with CuO, whose fusion temperature is low, the diffusion process is enhanced by solid state reactions with the presence of liquid phase. The process of reaction is better and the particle size is larger, which leads to the increase of sample density. In Figure 4, the shape of particles is nearly single crystal. Compound a(Å) b(Å) c(Å) α β γ V(Err or! Refere nce source not found. )3 LaFeO3 5,570 5,532 7,890 90 o 90o 90o 243,1 La(Fe0,6Ti0,4)O3 5,596 5,531 7,892 90 o 90o 90o 244,3 La(Fe0,5Ti0,5)O3 5,664 5,532 7,892 90 o 90o 90o 247,3 La(Fe0,4Co0,1Ti0,5)O3 5,672 5,532 7,896 90 o 90o 90o 247,8 La(Fe0,3Co0,2Ti0,5)O3 5,683 5,534 7,910 90 o 90o 90o 248,8 Temperature a(Err or! Refer ence sourc e not found. ) b(Erro r! Refere nce source not found.) c(Error ! Refere nce source not found.) α β γ V(Erro r! Refere nce source not found.) 3 12300C 5,586 5,531 7,885 90o 90o 90o 243,6 12500C 5,596 5,532 7,890 90o 90o 90o 244,3 EXTRAORDINARY MAGNETIC PROPERTIES OF LaFeO3 SYSTEM DOPED Ti, Co, Cu 35 According to Fig.5 and Table 3, all the samples behave as ferromagnetism. Among which, La(Fe0.4Cu0.1Ti0.5)O3 shows stronger ferromagnetism than two others samples. Its magnetic hysteresis loop is more vertical, which means it can be magnetized more easily [9-14]. Theoretically, magnetization of the sample will decrease when doping Cu into La(Fe0.5Ti0.5)O3 since ion Cu +1 and Cu+2 both show paramagnetism. However, magnetization of the sample increases drastically when doping Cu. This extraordinary phenomenon can be explained by the rapid increase of the sampling density when CuO is contained in the sample. Figure 6 and figure 7 is the M(T) loop of La(Fe0,3Co0,2Ti0,5)O3 measured at magnetic field 100 Oe and 1T respectively. The M(T) loop in Figure 6 is considered to be interesting as the magnetization is negative (M<0) in the temperature range from room temperature to about 2000C and increases as the temperature rises. We assume that since the magnetizing magnetic field is too small, the magnetizing energy is not big enough to create ferromagnetic order. It can only create an inducing magnetization, which is opposite to external magnetic field and negative same as the magnetization of diamagnetic material. When increasing the temperature, thermoenergy and magnetic energy will increase big enough to create ferromagnetic order. In this case, at the temperature higher than 2000C, the sample behaves as ferromagnetism and the magnetization is proportional to temperature by the Hopkinson effect (the M(T) loop at the temperature range higher than 2000C (Fig. 6)), from which the Curie temperature is established at about 5000C. In figure 7, magnetizing magnetic field 1Tesla is high enough to create ferromagnetic order at room temperature, thus the magnetization of sample at room temperature is positive and the Curie temperature is about 5000C [15-18]. Table 3. Magnetic hysteresis loop parameters of LaFeO3(a), La(Fe0,6Ti0,4)O3(b), La(Fe0,3Co0,2Ti0,5)O3(c) sintered at 1290 0C and La(Fe0.4Cu0.1Ti0.5)O3(d) sintered at 1250 0C. Hysteresis parameter LaFeO3 La(Fe0,6Ti0,4)O3 La(Fe0,3Co0,2Ti0,5)O3 La(Fe0.4Cu0.1Ti0.6)O3 Mm(emu/g) 0,310 0,210 0,420 1,560 Mr (emu/g) 0,010 0,021 0,025 0,082 Hc (KOe ) 5,7 18,2 5,3 0,15 S = Mr / Mm 0,032 0,10 0,06 0,05 36 NGUYEN THI THUY et al. Fig. 3a. SEM image of LaFeO3 sintered at 1290 0C Fig. 3b. SEM image of La(Fe0,6Ti0,4)O3 sintered at 12900C Fig. 3c. SEM image of La(Fe0,3Co0,2Ti0,5)O3 sintered at 12900C Fig. 4a. SEM image of La(Fe0,4Cu0,1Ti0,5)O3 sintered at 12300C Fig. 4b. SEM image of La(Fe0,4Cu0,1Ti0,5)O3 sintered at 12500C -20000 -10000 0 10000 20000 LaFeO3 M [ e m u /g ] H [Oe] -0,4 -0,2 0,0 0,2 0,4 -20000 -10000 0 10000 20000 -0,2 -0,1 0,0 0,1 0,2 La(Fe 0,6 Ti 0,4 )O 3 M [ e m u /g ] H [Oe] -20000 -10000 0 10000 20000 -2 -1 0 1 2 M [ e m u /g ] H [Oe] La(Fe 0,4 Cu 0,1 Ti 0,5 )O 3 -20000 -10000 0 10000 20000 -0,04 -0,02 0,00 0,02 0,04 M [ e m u /g ] H [Oe] La(Fe 0,3 Co 0,2 Ti 0,5 )O 3 EXTRAORDINARY MAGNETIC PROPERTIES OF LaFeO3 SYSTEM DOPED Ti, Co, Cu 37 0 100 200 300 400 500 600 -0,02 -0,01 0,00 0,01 0,02 T 0 (C) La(Fe 0,3 Co 0,2 Ti 0,5 )O 3 M [ e m u /g ] Fig. 6. M(T) loop of La(Fe0,3Co0,2Ti0,5)O3 measured at magnetic field H=100Oe 0 100 200 300 400 500 600 5.0x10 -3 1.0x10 -2 1.5x10 -2 2.0x10 -2 La(Fe 0,3 Cu 0,2 Ti 0,5 )O 3 M [ e m u /g ] T0(C) Fig. 7. M(T) loop of La(Fe0,3Co0,2Ti0,5)O3 measured at magnetic field H=1T 600400 5003002000 100 (d) T(oC) M [ e m u /g ] La(Fe 0,4 Cu 0,1 Ti 0,5 )O 3 0,0 0,5 1,0 1,5 Fig. 8. M(T) loop of La(Fe0.4Cu0.1Ti0.5)O3 measured at magnetic field H=100Oe Figure 8 is M(T) loop of La(Fe0.4Cu0.1Ti0.5)O3 measured at H=100 Oe. Although the magnetic field is low (as in the case of Fig.6), it is enough to make the magnetization a high positive value at room temperature because ferromagnetism of the sample is stronger and the sample can be magnetized more easily. The Curie temperature of the sample La(Fe0.4Cu0.1Ti0.5)O3 is about 450 0C. 4. CONCLUSIONS LaFeO3 system with Doped Ti, Co, Cu is manufactured successfully by using solid state reaction method. The manufactured samples have orthorhombic structure, theirs unit cell volumes increase once Ti, Co, Cu is doped into the sample. The crystal lattice deformation when doping is the main reason affecting the magnetic properties of samples. The size of the sample particles is quite homogeneous. The samples show ferromagnetic properties, among which La(Fe0.4Cu0.1Ti0,5)O3 shows the strongest ferromagnetic properties. 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