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K Hono - One of the best experts on this subject based on the ideXlab platform.
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Coercivity and its thermal stability of ndfeb hot deformed magnets enhanced by the eutectic grain boundary diffusion process
Acta Materialia, 2018Co-Authors: Lihua Liu, H Sepehriamin, T Ohkubo, Akira Kato, T Shoji, Noritsugu Sakuma, Xin Tang, T Schrefl, K HonoAbstract:Abstract Eutectic grain boundary diffusion process was applied to Nd Fe B hot-deformed magnet using Nd60Tb20Cu20 alloy, which resulted in a large Coercivity enhancement from 0.87 T to 2.57 T with a relatively small decrease in remanent magnetization from 1.50 T to 1.38 T. Improved temperature coefficient of Coercivity from −0.493%°C−1 to −0.328%/°C−1 led to a high Coercivity of 1.47 T at 150 °C. The partial formation of Tb-rich shell on the surface of platelet shaped Nd2Fe14B grains while maintaining their ultra-fine grain size is the reasons for the substantial enhancement of the Coercivity. Micromagnetic simulations suggested that a higher Coercivity can be obtained when Tb-rich shell covers the c-plane surface interface of the grains than that covering the side surface interfaces. Improvement of the thermal stability of Coercivity was found to be due to the exchange decoupling of Nd2Fe14B grains and the formation of (Nd,Tb)2Fe14B shell. In the frame of Kronmuller equation and based on the micromagnetic simulations, the improvement of the thermal stability of Coercivity is attributed to the decrease of Neff and increase of α induced by exchange decoupling of grains, as well as the additional decrease of Neff induced by the formation of high-Ha shell.
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Coercivity and its thermal stability of nd fe b hot deformed magnets enhanced by the eutectic grain boundary diffusion process
Acta Materialia, 2018Co-Authors: Lihua Liu, H Sepehriamin, T Ohkubo, Akira Kato, T Shoji, Noritsugu Sakuma, Xin Tang, T Schrefl, K HonoAbstract:Abstract Eutectic grain boundary diffusion process was applied to Nd Fe B hot-deformed magnet using Nd60Tb20Cu20 alloy, which resulted in a large Coercivity enhancement from 0.87 T to 2.57 T with a relatively small decrease in remanent magnetization from 1.50 T to 1.38 T. Improved temperature coefficient of Coercivity from −0.493%°C−1 to −0.328%/°C−1 led to a high Coercivity of 1.47 T at 150 °C. The partial formation of Tb-rich shell on the surface of platelet shaped Nd2Fe14B grains while maintaining their ultra-fine grain size is the reasons for the substantial enhancement of the Coercivity. Micromagnetic simulations suggested that a higher Coercivity can be obtained when Tb-rich shell covers the c-plane surface interface of the grains than that covering the side surface interfaces. Improvement of the thermal stability of Coercivity was found to be due to the exchange decoupling of Nd2Fe14B grains and the formation of (Nd,Tb)2Fe14B shell. In the frame of Kronmuller equation and based on the micromagnetic simulations, the improvement of the thermal stability of Coercivity is attributed to the decrease of Neff and increase of α induced by exchange decoupling of grains, as well as the additional decrease of Neff induced by the formation of high-Ha shell.
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Coercivity of the nd fe b hot deformed magnets diffusion processed with low melting temperature glass forming alloys
Journal of Magnetism and Magnetic Materials, 2016Co-Authors: U M R Seelam, H Sepehriamin, T Ohkubo, K Hono, Masao Yano, Akira Kato, T Akiya, Noritsugu SakumaAbstract:Abstract Nd- and Pr-based alloys with bulk glass forming ability and low melting temperatures, Nd 60 Al 10 Ni 10 Cu 20 and Pr 60 Al 10 Ni 10 Cu 20 , were used for grain boundary diffusion process to enhance the Coercivity of hot-deformed magnets. The Coercivity increment was proportional to the weight gain after the diffusion process. For the sample with 64% weight gain, the Coercivity increased up to 2.8 T, which is the highest value for bulk Nd–Fe–B magnets that do not contain heavy rare-earth elements, Dy or Tb. Approximately half of the intergranular regions were amorphous and the remaining regions were crystalline. Magnetic isolation of the Nd 2 Fe 14 B grains by the Nd-rich amorphous/crystalline intergranular phases is attributed to the large Coercivity enhancement. The Coercivity does not change after the crystallization of the intergranular phase, indicating that the Coercivity is not influenced by the strain at the interface with the crystalline intergranular phase.
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Coercivity enhancement of hot deformed nd fe b magnets by the eutectic grain boundary diffusion process
Journal of Alloys and Compounds, 2016Co-Authors: Lihua Liu, H Sepehriamin, T Ohkubo, Masao Yano, Akira Kato, T Shoji, K HonoAbstract:Abstract Nd-M (M = Al, Cu, Ga, Zn, Mn) alloys with compositions close to eutectic points were investigated as diffusion sources for the grain boundary diffusion process to hot-deformed Nd-Fe-B magnets. Coercivity enhancement was observed for most of the alloys. Among them, the sample processed with Nd 90 Al 10 exhibited the highest Coercivity of 2.5 T at room temperature. However, the sample processed with Nd 70 Cu 30 exhibited the highest Coercivity of 0.7 T at 200 ° C. Microstructural observations using scanning transmission electron microscope (STEM) showed that nonferromagnetic Nd-rich intergranular phase envelops the Nd 2 Fe 14 B grains after the diffusion process. Abnormal grain growth and the dissolution of Al into the Nd 2 Fe 14 B grains were observed in the sample processed with Nd 90 Al 10 , which explains its inferior thermal stability of Coercivity compared to the sample processed with Nd 70 Cu 30 . The Coercivity enhancement and poor thermal stability of the Coercivity of the Nd 90 Al 10 diffusion-processed sample are discussed based on microstructure studies by transmission electron microscopy.
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effect of carbon on the Coercivity and microstructure in fine grained nd fe b sintered magnet
Acta Materialia, 2015Co-Authors: T T Sasaki, T Ohkubo, M Sagawa, Y Une, H Kubo, K HonoAbstract:Abstract We have investigated the effect of carbon on the Coercivity and microstructure in fine-grained Nd–Fe–B sintered magnets fabricated by the pressless sintering method. The Coercivity of the sample with the carbon content of 730 ppm (low-C) was 1.59 T while that of the sample with 1500 ppm (high-C) was 1.44 T in the as-sintered state. The low-C sample exhibited a larger Coercivity increase by a post-sinter annealing, reaching the highest Coercivity of 1.85 T, while the high-C sample reached a lower Coercivity of 1.54 T. Detailed microstructure investigations using scanning electron microscopy, scanning transmission electron microscopy and atom probe tomography revealed that the high carbon content resulted in the formation of a Nd-carbide with a tetragonal structure and the reduction in the volume fraction of an α-Nd phase at triple junctions. This in turn decreased the Nd + Pr concentration in thin Nd-rich grain boundary phase, resulting in the lower Coercivity.
Bao-gen Shen - One of the best experts on this subject based on the ideXlab platform.
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cerium based rco5 r ce la0 35ce0 65 and misch metal type nanocrystalline hard magnetic materials with high Coercivity
APL Materials, 2019Co-Authors: Jeotikanta Mohapatra, Xuefeng Zhang, Tongyun Zhao, Fengxia Hu, Yongfeng Li, Bao-gen ShenAbstract:Nanocrystalline RCo5 (R = Ce, La0.35Ce0.65, and misch-metal noted as MM) ribbons with hexagonal crystal structure and an average grain size of 5 nm have been prepared via a one-step melt-spinning technique. Coercivity as high as 13.0, 13.8, and 10.9 kOe has been obtained at 300 K for the CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. High thermal stability is also achieved as shown by the high Coercivity of 9.3 kOe, 10.2 kOe, and 8.8 kOe at 400 K for CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. The Coercivity mechanism is studied by magnetization analysis and microstructural observations. The nanocrystalline grains promote a strong exchange interaction, as indicated by the positive δM and the relatively high remanence ratio (∼0.8). In addition, the temperature dependence of Coercivity of RCo5 ribbons shows the low Coercivity temperature coefficient of −0.2% to −0.25%/K.Nanocrystalline RCo5 (R = Ce, La0.35Ce0.65, and misch-metal noted as MM) ribbons with hexagonal crystal structure and an average grain size of 5 nm have been prepared via a one-step melt-spinning technique. Coercivity as high as 13.0, 13.8, and 10.9 kOe has been obtained at 300 K for the CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. High thermal stability is also achieved as shown by the high Coercivity of 9.3 kOe, 10.2 kOe, and 8.8 kOe at 400 K for CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. The Coercivity mechanism is studied by magnetization analysis and microstructural observations. The nanocrystalline grains promote a strong exchange interaction, as indicated by the positive δM and the relatively high remanence ratio (∼0.8). In addition, the temperature dependence of Coercivity of RCo5 ribbons shows the low Coercivity temperature coefficient of −0.2% to −0.25%/K.
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cerium based rco5 r ce la0 35ce0 65 and misch metal type nanocrystalline hard magnetic materials with high Coercivity
APL Materials, 2019Co-Authors: Jeotikanta Mohapatra, Xuefeng Zhang, Wen-liang Zuo, Tongyun Zhao, Jirong Sun, Ping J Liu, Bao-gen ShenAbstract:Nanocrystalline RCo5 (R = Ce, La0.35Ce0.65, and misch-metal noted as MM) ribbons with hexagonal crystal structure and an average grain size of 5 nm have been prepared via a one-step melt-spinning technique. Coercivity as high as 13.0, 13.8, and 10.9 kOe has been obtained at 300 K for the CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. High thermal stability is also achieved as shown by the high Coercivity of 9.3 kOe, 10.2 kOe, and 8.8 kOe at 400 K for CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. The Coercivity mechanism is studied by magnetization analysis and microstructural observations. The nanocrystalline grains promote a strong exchange interaction, as indicated by the positive δM and the relatively high remanence ratio (∼0.8). In addition, the temperature dependence of Coercivity of RCo5 ribbons shows the low Coercivity temperature coefficient of −0.2% to −0.25%/K.
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Cerium-based RCo5 (R = Ce, La0.35Ce0.65, and misch-metal) type nanocrystalline hard magnetic materials with high Coercivity
APL Materials, 2019Co-Authors: Wen-liang Zuo, Jeotikanta Mohapatra, Xuefeng Zhang, Tongyun Zhao, Jirong Sun, J. Ping Liu, Bao-gen ShenAbstract:Nanocrystalline RCo5 (R = Ce, La0.35Ce0.65, and misch-metal noted as MM) ribbons with hexagonal crystal structure and an average grain size of 5 nm have been prepared via a one-step melt-spinning technique. Coercivity as high as 13.0, 13.8, and 10.9 kOe has been obtained at 300 K for the CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. High thermal stability is also achieved as shown by the high Coercivity of 9.3 kOe, 10.2 kOe, and 8.8 kOe at 400 K for CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. The Coercivity mechanism is studied by magnetization analysis and microstructural observations. The nanocrystalline grains promote a strong exchange interaction, as indicated by the positive δM and the relatively high remanence ratio (∼0.8). In addition, the temperature dependence of Coercivity of RCo5 ribbons shows the low Coercivity temperature coefficient of −0.2% to −0.25%/K.
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Coercivity of isotropic nanocrystalline Pr12Fe82B6 ribbons
Physical Review B, 2002Co-Authors: Hong-wei Zhang, Chuanbing Rong, Jian Zhang, Shao-ying Zhang, Bao-gen ShenAbstract:The magnetization reversal has been examined by the temperature dependence of the Coercivity, the initial magnetization curve, minor hysteresis loops, and thermal activation in isotropic nanocrystalline Pr-Fe-B ribbons. The Coercivity mechanism is found to vary with temperature. At 20 K, the Coercivity is mainly determined by strong pinning (by random inhomogeneities); while at room temperature it is mainly controlled by the nucleation of domain and localized pinning at grain boundaries. The influence of the grain-boundary character on magnetic hardening and the temperature dependence of intergrain exchange coupling and anisotropy have been investigated to discuss the Coercivity mechanism.
Wen-liang Zuo - One of the best experts on this subject based on the ideXlab platform.
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cerium based rco5 r ce la0 35ce0 65 and misch metal type nanocrystalline hard magnetic materials with high Coercivity
APL Materials, 2019Co-Authors: Jeotikanta Mohapatra, Xuefeng Zhang, Wen-liang Zuo, Tongyun Zhao, Jirong Sun, Ping J Liu, Bao-gen ShenAbstract:Nanocrystalline RCo5 (R = Ce, La0.35Ce0.65, and misch-metal noted as MM) ribbons with hexagonal crystal structure and an average grain size of 5 nm have been prepared via a one-step melt-spinning technique. Coercivity as high as 13.0, 13.8, and 10.9 kOe has been obtained at 300 K for the CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. High thermal stability is also achieved as shown by the high Coercivity of 9.3 kOe, 10.2 kOe, and 8.8 kOe at 400 K for CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. The Coercivity mechanism is studied by magnetization analysis and microstructural observations. The nanocrystalline grains promote a strong exchange interaction, as indicated by the positive δM and the relatively high remanence ratio (∼0.8). In addition, the temperature dependence of Coercivity of RCo5 ribbons shows the low Coercivity temperature coefficient of −0.2% to −0.25%/K.
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Cerium-based RCo5 (R = Ce, La0.35Ce0.65, and misch-metal) type nanocrystalline hard magnetic materials with high Coercivity
APL Materials, 2019Co-Authors: Wen-liang Zuo, Jeotikanta Mohapatra, Xuefeng Zhang, Tongyun Zhao, Jirong Sun, J. Ping Liu, Bao-gen ShenAbstract:Nanocrystalline RCo5 (R = Ce, La0.35Ce0.65, and misch-metal noted as MM) ribbons with hexagonal crystal structure and an average grain size of 5 nm have been prepared via a one-step melt-spinning technique. Coercivity as high as 13.0, 13.8, and 10.9 kOe has been obtained at 300 K for the CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. High thermal stability is also achieved as shown by the high Coercivity of 9.3 kOe, 10.2 kOe, and 8.8 kOe at 400 K for CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. The Coercivity mechanism is studied by magnetization analysis and microstructural observations. The nanocrystalline grains promote a strong exchange interaction, as indicated by the positive δM and the relatively high remanence ratio (∼0.8). In addition, the temperature dependence of Coercivity of RCo5 ribbons shows the low Coercivity temperature coefficient of −0.2% to −0.25%/K.
Jeotikanta Mohapatra - One of the best experts on this subject based on the ideXlab platform.
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cerium based rco5 r ce la0 35ce0 65 and misch metal type nanocrystalline hard magnetic materials with high Coercivity
APL Materials, 2019Co-Authors: Jeotikanta Mohapatra, Xuefeng Zhang, Tongyun Zhao, Fengxia Hu, Yongfeng Li, Bao-gen ShenAbstract:Nanocrystalline RCo5 (R = Ce, La0.35Ce0.65, and misch-metal noted as MM) ribbons with hexagonal crystal structure and an average grain size of 5 nm have been prepared via a one-step melt-spinning technique. Coercivity as high as 13.0, 13.8, and 10.9 kOe has been obtained at 300 K for the CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. High thermal stability is also achieved as shown by the high Coercivity of 9.3 kOe, 10.2 kOe, and 8.8 kOe at 400 K for CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. The Coercivity mechanism is studied by magnetization analysis and microstructural observations. The nanocrystalline grains promote a strong exchange interaction, as indicated by the positive δM and the relatively high remanence ratio (∼0.8). In addition, the temperature dependence of Coercivity of RCo5 ribbons shows the low Coercivity temperature coefficient of −0.2% to −0.25%/K.Nanocrystalline RCo5 (R = Ce, La0.35Ce0.65, and misch-metal noted as MM) ribbons with hexagonal crystal structure and an average grain size of 5 nm have been prepared via a one-step melt-spinning technique. Coercivity as high as 13.0, 13.8, and 10.9 kOe has been obtained at 300 K for the CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. High thermal stability is also achieved as shown by the high Coercivity of 9.3 kOe, 10.2 kOe, and 8.8 kOe at 400 K for CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. The Coercivity mechanism is studied by magnetization analysis and microstructural observations. The nanocrystalline grains promote a strong exchange interaction, as indicated by the positive δM and the relatively high remanence ratio (∼0.8). In addition, the temperature dependence of Coercivity of RCo5 ribbons shows the low Coercivity temperature coefficient of −0.2% to −0.25%/K.
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cerium based rco5 r ce la0 35ce0 65 and misch metal type nanocrystalline hard magnetic materials with high Coercivity
APL Materials, 2019Co-Authors: Jeotikanta Mohapatra, Xuefeng Zhang, Wen-liang Zuo, Tongyun Zhao, Jirong Sun, Ping J Liu, Bao-gen ShenAbstract:Nanocrystalline RCo5 (R = Ce, La0.35Ce0.65, and misch-metal noted as MM) ribbons with hexagonal crystal structure and an average grain size of 5 nm have been prepared via a one-step melt-spinning technique. Coercivity as high as 13.0, 13.8, and 10.9 kOe has been obtained at 300 K for the CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. High thermal stability is also achieved as shown by the high Coercivity of 9.3 kOe, 10.2 kOe, and 8.8 kOe at 400 K for CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. The Coercivity mechanism is studied by magnetization analysis and microstructural observations. The nanocrystalline grains promote a strong exchange interaction, as indicated by the positive δM and the relatively high remanence ratio (∼0.8). In addition, the temperature dependence of Coercivity of RCo5 ribbons shows the low Coercivity temperature coefficient of −0.2% to −0.25%/K.
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Cerium-based RCo5 (R = Ce, La0.35Ce0.65, and misch-metal) type nanocrystalline hard magnetic materials with high Coercivity
APL Materials, 2019Co-Authors: Wen-liang Zuo, Jeotikanta Mohapatra, Xuefeng Zhang, Tongyun Zhao, Jirong Sun, J. Ping Liu, Bao-gen ShenAbstract:Nanocrystalline RCo5 (R = Ce, La0.35Ce0.65, and misch-metal noted as MM) ribbons with hexagonal crystal structure and an average grain size of 5 nm have been prepared via a one-step melt-spinning technique. Coercivity as high as 13.0, 13.8, and 10.9 kOe has been obtained at 300 K for the CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. High thermal stability is also achieved as shown by the high Coercivity of 9.3 kOe, 10.2 kOe, and 8.8 kOe at 400 K for CeCo5, La0.35Ce0.65Co5, and MMCo5 ribbons, respectively. The Coercivity mechanism is studied by magnetization analysis and microstructural observations. The nanocrystalline grains promote a strong exchange interaction, as indicated by the positive δM and the relatively high remanence ratio (∼0.8). In addition, the temperature dependence of Coercivity of RCo5 ribbons shows the low Coercivity temperature coefficient of −0.2% to −0.25%/K.
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coherent magnetization reversal and high magnetic Coercivity in co nanowire assemblies
Journal of Magnetism and Magnetic Materials, 2017Co-Authors: Kinjal Gandha, Jeotikanta MohapatraAbstract:Abstract Nanowires (NWs) of single crystalline hcp Co with length from 200 to 530 nm and diameter from 8 to 20 nm (corresponding to the aspect ratio from 10 to 66) are synthesized via a solvothermal method by controlling the Co-precursor to amine mole concentration. The increased aspect ratio leads to enhanced Coercivity of randomly oriented Co NWs up to an optimum value of 6.7 kOe, for the NWs of average length 200 nm and average diameter 15 nm (aspect ratio ∼13). Alignment of the NWs in a magnetic field leads to further enhanced Coercivity up to a doubled value of 12.5 kOe at 300 K. The high magnetic Coercivity achieved in the random and aligned assemblies is due to both the magnetocrystalline anisotropy and the shape anisotropy. For a better understanding of the Coercivity mechanism of the NWs, angular dependence of the Coercivity has been experimentally investigated for the aligned NW assemblies and the corresponding magnetization reversal mode is determined to be a coherent reversal mode according to an analytical simulation based on the Stoner-Wohlfarth model.
G C Hadjipanayis - One of the best experts on this subject based on the ideXlab platform.
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Coercivity enhancement in heavy rare earth free ndfeb magnets by grain boundary diffusion process
Applied Physics Letters, 2018Co-Authors: D Salazar, A Martincid, Rajasekhar Madugundo, J M Barandiaran, G C HadjipanayisAbstract:Grain boundary diffusion of a Pr3(Co,Cu) eutectic alloy has been performed for Coercivity enhancement on Nd-lean Nd10Fe84B6 nanocrystalline ribbons. The Coercivity increases from 0.5 T to 2.5 T after 6 h of infiltration at 600 °C. High resolution electron microscopy and energy dispersive X-ray spectroscopy show that the excess α-Fe present in the initial samples diminishes during infiltration, giving rise to the formation of a Rare Earth-rich RE-Fe inter-boundary phase and a layer of (Nd,Pr)2Fe14B close to the surface of the hard magnetic grains. Such a microstructure favours the Coercivity by increasing the nucleation field for reversal magnetization and providing magnetically isolated/decoupled hard grains.Grain boundary diffusion of a Pr3(Co,Cu) eutectic alloy has been performed for Coercivity enhancement on Nd-lean Nd10Fe84B6 nanocrystalline ribbons. The Coercivity increases from 0.5 T to 2.5 T after 6 h of infiltration at 600 °C. High resolution electron microscopy and energy dispersive X-ray spectroscopy show that the excess α-Fe present in the initial samples diminishes during infiltration, giving rise to the formation of a Rare Earth-rich RE-Fe inter-boundary phase and a layer of (Nd,Pr)2Fe14B close to the surface of the hard magnetic grains. Such a microstructure favours the Coercivity by increasing the nucleation field for reversal magnetization and providing magnetically isolated/decoupled hard grains.
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microstructure and high temperature magnetic properties of sm co cu fe zr z z 6 7 9 1 permanent magnets
Journal of Applied Physics, 1999Co-Authors: J F Liu, Y Zhang, D Dimitrov, G C HadjipanayisAbstract:The effect of ratio z on the high temperature magnetic properties of Sm(Co, Fe, Cu, Zr)z magnets have been examined in a range of ratio z values from 6.7 to 9.1. Reasonably high Coercivity at room temperature has been achieved in all the magnets. It was found that the lower the ratio z, the smaller the temperature coefficient of Coercivity. When the ratio z=7.0, a temperature coefficient of Coercivity of −0.03%/°C can be achieved, which is more than eight times smaller than the magnet with z=8.5. A Coercivity of more than 10 kOe has been obtained at 773 K for the newly developed magnets, which is believed to be the highest Coercivity at 773 K ever reported. Transmission electron microscope studies showed that the cell size decreases with the decrease of the ratio z, while the density of lamella phase remains almost the same. This suggests that smaller cell size leads to a smaller temperature coefficient of intrinsic Coercivity.
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abnormal temperature dependence of intrinsic Coercivity in sm co fe cu zr z powder materials
Applied Physics Letters, 1998Co-Authors: J F Liu, D Dimitrov, T Chui, G C HadjipanayisAbstract:The intrinsic Coercivity Hci in Sm(CobalCuxFe0.1Zr0.033)z powder materials was found to increase with increasing temperature when Cu content x=0.048, but to decrease when Cu content x⩾0.068. This abnormal behavior, which is also reversible, was found in a series of samples with various ratios z. The field dependence of the intrinsic Coercivity suggests that the bonded magnets were fully saturated with an applied field of 20 kOe. The exposure to higher temperatures did not change the room temperature value of Coercivity. This indicates that the microstructure does not change during the measurement from 573 to 773 K. The change of Coercivity mechanism was found to be responsible for this abnormal temperature behavior. Monte Carlo simulation showed that the Coercivity increases (decreases) with increasing temperature for the repulsive (attractive) cell boundary, which is consistent with the experimental results.