United States

In recent years, the driving frequency of electric equipment has increased, and we need to reduce eddy current loss to apply typical metallic soft magnetic materials into high-frequency driving equipment. As a practical method to reduce the loss is a reduction in the thickness, we recently reported a fabrication process of Fe-Ni thin films (&lt; 10 μm) using an electroless plating method [1]. Although many reports for electroless deposited Fe-Ni films, as well as ours, employed conductive substrates [2-3], the conductive substrates are not suitable since eddy current also flows in the substrates. We, therefore, focused on the polyimide (PI) used as a non-conductive substrate and investigated a fabrication process of Fe-Ni films using the PI substrate.&lt;br&gt;
Since the PI does not have catalytic activity for the deposition of Fe-Ni films, we investigated a chemical metallization process of PI [4]. First, we immersed the PI sheet in a KOH solution and then in an AgNO3 one. By these immersions, the PI sheet obtains catalytic activity. The details of our electroless plating process are described in Ref. [1].&lt;br&gt;
To obtain suitable conditions for the metallization of the PI surface, we investigated the effect of immersion time in KOH and AgNO3 on the film thickness. Figure 1 shows the thickness as a function of the immersion time in each solution. The thickness slightly increased with increasing the immersion time in AgNO3, and we observed the correlation between thickness and the immersion time in KOH, implying that the immersion time in KOH is more important than that for AgNO3.&lt;br&gt;
Figure 2 shows the coercivity of the films as a function of thickness. We changed the thickness by adjusting the DMAB concentration or the deposition time. In our experimental conditions, the coercivity increased with increasing the thickness due to an increase in the roughness, and the value of coercivity was almost the same as previously reported ones (Hc =30-96 A/m) using conductive substrates [1-3.5]. We, therefore, concluded that the Fe-Ni films with low coercivity could be obtained by the optical metallization of the PI surface.&lt;br&gt;
**References:**&lt;br&gt;[1] T. Yanai et al., AIP Advances, Vol.10 ,#015047 (2020)&lt;br&gt;
[2] R. Anthony et al., Applied Surface Science, Vol.357 , pp.385-390 (2015)&lt;br&gt;
[3] M. Takai et al., IEICTE Trans. Electron., Vol.E78-C , pp. 1530-1535 (1995)&lt;br&gt;
[4] G. Stéphane et al., Applied surface science, Vol.307, pp.716-723 (2014)&lt;br&gt;
[5] T. Yokoshima et al., Journal of Electroanalytical Chemistry, Vol.491 , pp.197-202 (2000)&lt;br&gt;

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MMM 2022

Magnetic properties of Fe Ni films deposited on a non

In recent years, the driving frequency of electric equipment has increased, and we need to reduce eddy current loss to apply typical metallic soft magnetic materials into high-frequency driving equipment. As a practical method to reduce the loss is a reduction in the thickness, we recently reported a fabrication process of Fe-Ni thin films (< 10 μm) using an electroless plating method [1]. Although many reports for electroless deposited Fe-Ni films, as well as ours, employed conductive substrates [2-3], the conductive substrates are not suitable since eddy current also flows in the substrates. We, therefore, focused on the polyimide (PI) used as a non-conductive substrate and investigated a fabrication process of Fe-Ni films using the PI substrate. 
Since the PI does not have catalytic activity for the deposition of Fe-Ni films, we investigated a chemical metallization process of PI [4]. First, we immersed the PI sheet in a KOH solution and then in an AgNO3 one. By these immersions, the PI sheet obtains catalytic activity. The details of our electroless plating process are described in Ref. [1]. 
To obtain suitable conditions for the metallization of the PI surface, we investigated the effect of immersion time in KOH and AgNO3 on the film thickness. Figure 1 shows the thickness as a function of the immersion time in each solution. The thickness slightly increased with increasing the immersion time in AgNO3, and we observed the correlation between thickness and the immersion time in KOH, implying that the immersion time in KOH is more important than that for AgNO3. 
Figure 2 shows the coercivity of the films as a function of thickness. We changed the thickness by adjusting the DMAB concentration or the deposition time. In our experimental conditions, the coercivity increased with increasing the thickness due to an increase in the roughness, and the value of coercivity was almost the same as previously reported ones (Hc =30-96 A/m) using conductive substrates [1-3.5]. We, therefore, concluded that the Fe-Ni films with low coercivity could be obtained by the optical metallization of the PI surface. 
**References:** [1] T. Yanai et al., AIP Advances, Vol.10 ,#015047 (2020) 
[2] R. Anthony et al., Applied Surface Science, Vol.357 , pp.385-390 (2015) 
[3] M. Takai et al., IEICTE Trans. Electron., Vol.E78-C , pp. 1530-1535 (1995) 
[4] G. Stéphane et al., Applied surface science, Vol.307, pp.716-723 (2014) 
[5] T. Yokoshima et al., Journal of Electroanalytical Chemistry, Vol.491 , pp.197-202 (2000) 

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poster

#### Welcome to the 67th Annual Conference on Magnetism and Magnetic Materials, MMM 2022!

The Conference was held from October 31 to November 4 and offers both in-person and on-demand content.

MMM 2022 is sponsored jointly by AIP Publishing and the IEEE Magnetics Society. Members of the international scientific and engineering communities interested in recent developments in fundamental and applied magnetism are invited to attend and contribute to the technical sessions. The technical program will include invited and contributed papers in oral and poster sessions, invited symposia, a tutorial, and several special sessions. This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

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In recent years, metallic soft magnetic materials, which can be used at high frequency, have been strongly required due to the development of power electronics techniques. When driving the metallic materials at a high frequency, we need to reduce the thickness or control the magnetization process (the anisotropy) to reduce eddy current loss. In the present study, we focused on an electroplating method to prepare thin ribbons and a bilayer structure to control the direction of anisotropy using the magnet elastic effect.
To construct a bilayer structure, we firstly electroplated 8 μm-thick Fe6Ni94 films on a stainless substrate and then electroplated 8 μm-thick Fe56Ni44 films. The plating bath and conditions were almost the same as ref [1]. Figure 1 shows a schematic representation of the electroplating, and we prepared 140 mm-long bilayer films. After electroplating, the bilayer film was peeled off from the substrate. The ribbon (peeled film) formed into a toroidal core (D = 10 mm).
Figure 2 shows the hysteresis loop of the core, and the difference between the loops is the inside layer. The blue and red loops are for the inside layer of Fe6Ni94 and Fe56Ni44, respectively. An obvious difference was observed between the two loops. It is well-known that the magnetostriction constant of Fe-Ni alloys depends on the composition. The sing of magnetostriction constant for Ni-rich phase such as Fe6Ni94 is negative, whereas Fe-rich one such as Fe56Ni44 is positive. When the ribbon formed a toroidal shape, bending stress is induced in the ribbon. The stress of the outer side and the inner one is tension and compression, respectively. In the case of the inside layer of Fe56Ni44, the directions of the induced anisotropy are perpendicular to the ribbon axis for both phases, indicating that the easy axis is perpendicular to the ribbon axis. Consequently, the permeability and the hysteresis loss decrease. As the perpendicular anisotropy is effective in reducing the eddy current loss, we found that thin bilayer ribbons, which consist of two phases with positive and negative magnetostriction, are an attractive structure for high-frequency applications. 
**References:** [1]T. Yanai, J. Kaji, K. Koda, K. Takashima, M. Nakano, H. Fukunaga, “Magnetic Properties of Exchange-Coupled Fe-Ni/Fe22Ni78 Double-Layered Thick Films”, IEEE Transactions on Magnetics, 54 (2018) #2002503. 

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Soft magnetic bilayer thin ribbons prepared using an electroplating method

With the development of the 5G applications, micrometer and millimeter microwaves have been full filling the space around people. They not only interfere with tons of electronic devices but damage human health as well. To combat these problems, there is an urgent need for microwave absorption materials. However, most of the research on microwave absorption materials stays within the 2~18GHz frequency range, while the 5G millimeter microwave’s frequency can reach up to 24GHz or higher. Thus, more studies of microwave absorption properties in a higher frequency band are necessary. In this work, we report the microwave absorption properties of several soft magnetic composites in frequency up to 40GHz. Common materials such as iron, Y2Fe16Si, Ce2Fe17N3-δ, La2Fe4Co10B micron powders which experience excellent microwave absorption properties in 2~18GHz are included. Within 2~40GHz, the reflection loss(RL) of iron/paraffin, Y2Fe16Si/paraffin, Ce2Fe17N3-δ/paraffin and La2Fe4Co10B /paraffin composites could reach -46.2dB, -71.4dB, -49.1dB, and -49.0dB, respectively. And their effective absorption bandwidth(RL<-10dB) could reach 16.9GHz, 8.53GHz, 10.08GHz, and 7.4GHz, respectively. Though the measurements are extended to 40GHz, the RL of most of these materials could not maintain a low level at 40GHz, which is restricted by the cutoff frequencies of the materials. The measured data shows that these soft magnetic composites are good candidates for high-frequency microwave absorption materials, while exploring magnetic materials with further higher cutoff frequencies may result in a better performance. 
**References:** Hu, Q. W., Qiao, G. Y., Yang, W. Y. et al., J. Phys. D: Appl. Phys., Vol. 53, p.115001 (2020) 
Qiao, G. Y., Yang, W. Y., Lai, Y. F. et al., Mater. Res. Express., Vol. 6, p.016103 (2019) 
Zuo, W. L., Qiao, L., Chi, X. et al., J. Alloys Compd., Vol. 509, p.6359-6363 (2011) 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/f708b4db425d125194f5d0dce657f7a5.png) 
Fig.1 The RL curves with the broadest effective absorption bandwidth of different composites. 
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Fig.2 The RL curves with the minimum RL of different composites.

The microwave absorption properties of several soft magnetic materials in frequency up to 40GHz

Motor-driven systems are estimated to use over 40% of all global electricity consumption, giving rise to over 6 Gt of CO2 emissions [1]. To reduce the impact, motors should have higher efficiency. Electrical steels, Fe-Si which have low iron losses are commonly used as soft magnetic materials for motors but higher Bs materials have been desired for higher power density motors. It is well known that Fe-Co alloys have the highest Bs among bulk, stable materials. In fact, Permendur, 49Fe-49Co-2V (mass %) is already used in some high-performance motors, since it has a good soft magnetic properties. However, the drawbacks of Permendur are poor workability owing to the existence of a the brittle B2 phase (ordered phase) . In this study, we first conducted neutron diffraction measurements on the Fe-Co alloys with different Co contents to check the existence of the B2 phase in these alloys. And then, the effect of Si/Al addition on magnetic properties of 82Fe-18Co alloy was investigated in order to improve the soft magnetic properties.

Experimental Procedures 
Four samples with different Co contents (49Fe-49Co-2V, 73Fe-27Co, 82Fe-18Co, and 95Fe-5Co) were prepared through melting, casting, forging and annealing processes. The neutron diffraction study was conducted with iMATERIA spectrometer at the Materials and Life Sciences Facility at the J-PARC (Japan Proton Accelerator Research Complex). For the study of Si/Al addition, 0.2 mm-thick sheets with the addition of Si/Al in the range of 0~1.75 mass% were prepared by melting, casting process, followed by forging, annealing, hot and cold rolling processes. Magnetic properties were measured with a BH-tracer.

Results 
The result showed that 49Fe-49Co-2V and 73Fe-27Co alloys contained the B2 phase. On the other hand, 82Fe-18Co and the 95Fe-5Co did not contain B2, which suggests that these two alloys will likely to have good workability. Therefore, we chose 82Fe-18Co alloy for the investigation of Si/Al addition. Fig. 1 shows the soft magnetic properties of 82Fe-18Co with and without Si/Al addition. It was found that the small addition of Si/Al reduced the iron loss while maintaining high Bs. 
**References:** [1] Paul Waide & Conrad U. Brunner et al., IEA Energy Efficiency Series, Working Paper, 2011.

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Fig. 1 Effect of Si and Al addition on the soft magnetic properties of Fe-18Co alloy

Effect of Si/Al addition on magnetic properties of Fe Co alloy

Motor cores usually operate at high temperatures, and the temperature affects their magnetic properties. It has been shown that the iron loss of 3.5% silicon steel decreases with the increase of temperature, and a model of iron loss considering the effect of temperature is proposed[1-2], but this model is not applicable to high silicon steel. It is reported that the iron loss of 6.5% silicon steel increases with the temperature[3]. Therefore, the study on the evolution of the temperature-dependent iron loss of silicon steel with different Si contents is particularly important, and there are few studies in this area. 
In the second part of this paper, the magnetic properties of silicon steels with different Si contents (2.5%, 3.5%, 4.5%, 5.5%, 6.5%) were tested at variable temperatures (-70°C-200°C) using a self-built multi-physical field coupling test system and non-standard ring sample test method, as shown in Fig 1.Some of the experimental results are shown in Fig 2, which reveal variation of iron loss law of silicon steel with different Si content under the effect of temperature, and explain the reason of this phenomenon from the internal microstructure of the material. The third part of this paper uses the above experimental data to reconstruct the loss model for a 6.5% silicon steel. The correlation analysis of temperature effects on eddy current losses and hysteresis losses of high silicon steel is carried out respectively, and the temperature-dependent loss coefficients are added to the corresponding mathematical model. The fourth part of this paper compares the experimental test data of high silicon steel loss, the calculated data of traditional loss model and the calculated data of this loss model to analyze their error accuracy, and finally verifies that for the loss calculation of high silicon steel, the proposed iron loss model is more accurate than the traditional calculation model.
Finally, this study will be of greater guidance for the design of subsequent high-silicon steel motors. 
**References:** [1] J. Q. Chen, D. Wang, and S. W. Cheng,“Modeling of temperature effects on magnetic property of non-oriented silicon steel lamination,” vol.51, no.11, Nov. 1, 2015. 
[2] N. Takahashi, M. Morishita, D. Miyagi, “Examination of magnetic properties of magnetic materials at high temperature using a ring specimen,”,vol. 46, no. 2, pp. 548–551, Feb.2010. 
[3] Ou, J, Liu, Y, Breining, P, Experimental Characterization and Feasibility Study on High Mechanical Strength Electrical Steels for High-Speed Motors Application. 57(1), 284-293. 

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Fig.1 Multiphysics coupled magnetic performance testing system and test sample 
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Fig.2 (left) Iron loss curves at different temperatures. (right) Variation of iron loss with temperature

Study on the Loss Characteristics of Silicon Steel with Different Si Content Considering the Effect of Temperature

Studying the magnetic properties of the Grain-Oriented(GO) electrical steel under different stresses in a wide frequency range is of great significance for improving the energy conversion efficiency of the motors or transformers. Residual bending stress can cause deterioration of the magnetic properties of the motor and lead to an increase in core losses[1]. However, only the effect of bending stress on the magnetic properties of GO electrical steel sheets at 50 Hz has been studied so far, and the magnetic properties at higher frequencies magnetization under bending stress is still unclear[2]. Aiming at this problem, the magnetic properties of GO electrical steel sheet under different bending stress up to 1kHz is investigated by developing a measuring system under different curvature loading mechanisms. 
II Method and Discussion 
For investigating the magnetic properties of the GO steel sheet under different bending stress, the single sheet specimen to be measured were bended into different radius of curvatures as shown in Fig.1. Because of the deterioration of the magnetic characteristics caused by the bend of the sample, it is very difficult to maintain the sinusoidal waveform for standardized testing in the measurement process. A robust digital control algorithm in the frequency domain with a normalized dual-loop control loops is proposed. Fig.2 shows the some measuring results of GO steel B27R090. It can be found that with the increase of bending stress, the loss increases significantly and the higher the frequency, the greater the influence of bending stress is found. 
III Conclusion 
The magnetic properties of electrical steel under different bending stress over a wide frequency range are measured by the proposed measuring system with a normalized frequency domain dual-loop feedback control algorithm in this paper. Obtained results show that the bending stress of electrical steel sheet has a great influence on the iron loss, and the influence becomes more obvious with the increase of frequency. 
**References:** [1] T. Wang et al . Fabrication and Experimental Analysis of an Axially Laminated Flux-Switching Permanent-Magnet Machine [J]. IEEE Transactions on Industrial Electronics, vol. 64, no. 2, pp. 1081-1091, Feb. 2017. 
[2] H. Hagihara, Y. Takahashi, K. Fujiwara, Y. Ishihara and T. Masuda. Magnetic Properties Evaluation of Grain-Oriented Electrical Steel Sheets Under Bending Stress [J]. IEEE Transactions on Magnetics, vol. 50, no. 4, pp. 1-4, April 2014, Art no. 2002104. 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/0103dfa4eae026846d34cfe7749fc6c8.png) 
Fig.1. Magnetic properties measurement system for electrical steel under bending stress and dual-loop control algorithm used. 
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Fig.2. Measurement results of electrical steel at different bending stresses.

Measurement of magnetic properties of grain oriented electrical steel under bending stress in a wide frequency range

Accurate calculation of hysteresis properties of magnetic materials is of great significance for the optimal design of electromagnetic devices. At the state of the art, the J-A model is widely used in the FEM procedures as it is easy to implement. However, the existing J-A models relying on the parameters identified by the static limiting hysteresis loops can only ensure the accurate calculation of grain-oriented (GO) silicon steel sheets at high magnetic densities, which have relatively poor calculation accuracy at low magnetic densities[1]. Aiming at this problem, this paper proposes an improved J-A model, which can accurately and quickly calculate the global hysteresis loops of GO silicon steel sheets with only a small amount of data. 
II Method and Discussion 
As shown in Fig. 1, an improved anisotropic J-A model suitable for GO silicon steel sheets is proposed introducing the some variable parameters. To solve the problem of low calculation accuracy when the magnetized state of the material is far from saturation, a damping factor R is introduced to correct the irreversible changing susceptibility of the J-A model. Meanwhile, the pinning coefficient k and domain flexing coefficient c of the J-A model are assumed that should be changed with the magnetic flux density B. It can be seen from Fig.2 (a, b, c) that the parameters k, c, and R have a good functioning relationship with the magnetic flux density B, so the parameters under the remaining magnetic flux densities can be quickly obtained. The velocity-controlled particle swarm (VCPSO) algorithm is used to identify various parameters[2]. The calculation results are shown in Fig 2 (d), which are in good agreement with the experimental data. 
III Conclusion 
This paper presents an improved anisotropic J-A model by introducing a damping factor R and considering the parameter R, k and c are as a function of magnetic flux densities. Obtained results show that the proposed model can accurately and quickly simulate the global hysteresis characteristic of GO silicon steel sheets. 
**References:** [1] Podbereznaya I, Pavlenko A . Accounting for dynamic losses in the Jiles-Atherton model of magnetic hysteresis - ScienceDirect[J]. Journal of Magnetism and Magnetic Materials, 2020, 513. 
[2] Chen L , Yi Q , Tong B , et al. Parameter identification of Preisach model based on velocity-controlled particle swarm optimization method[J]. AIP Advances, 2021, 11(1):015022. 

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Fig.1. Improved J-A Model Calculation Process 
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Fig.2. (a) Parameter k=f(B). (b) Parameter c=f(B). (c) Parameter R=f(B). (d) The simulation curve is compared with the measured data.

Accurate calculation of global hysteresis properties of grain oriented silicon steel based on an improved J

Axial flux motors for aviation systems operate at high altitudes, and the initial operating temperature of the motor is low, but due to the thin air, the motor temperature rise is high and the stator material temperature variation range is large[1], especially the segmented stator is close to the motor winding coil, and the thermal stress has a non-negligible effect on its material[2]. The segmented stator laminated magnetic energy model has been extensively studied in past researches, and no research has been proposed to consider the magnetic energy model of the laminated structure under the thermal stress of the material.
When the temperature changes, the segmented stator is not completely free to expand and contract due to the external constraints and the mutual constraints between the internal parts, thus generating thermal stresses [3]. Previous studies have shown that the temperature itself affects the magnetic properties of the material. In this paper, we intend to analyze the magnetic properties of the material by means of a coupled material multiphysics field testbed, and to divide the temperature-induced effects into the effects of temperature on the inherent properties of the material itself and the effects of thermal stresses induced by temperature changes on grain-oriented silicon steel, and to separate them equivalently. In this paper, a comparative analysis of the stator with different thicknesses of grain-oriented silicon steel is carried out, and the deformation of different stator materials under thermal stress is calculated by finite elements. Finally, the thermal stress effect percentage is tested experimentally. It is found that the use of thinner oriented silicon steel material will greatly reduce the effect of thermal stress on its magnetic properties. 
**References:** [1] Paredes J A, Saito C, Abarca M, et al. Study of effects of high-altitude environments on multicopter and fixed-wing UAVs' energy consumption and flight time[C]//2017 13th IEEE Conference on Automation Science and Engineering (CASE). IEEE, 2017: 1645-1650. 
[2] Wu Y, Ming T, Li X, et al. Numerical simulations on the temperature gradient and thermal stress of a thermoelectric power generator[J]. Energy conversion and management, 2014, 88: 915-927. 
[3] Yong L, Liang W, Qian W, et al. Calculation of deformation and material stress of a rotary voice coil motor used in aerospace[J]. Journal of Computational and Theoretical Nanoscience, 2015, 12(11): 4499-4505. 

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Fig. 1 Multi-physics field testing of two materials 
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Fig. 2 Simulation and physical model

Analysis of the Stator Magnetic Properties of an Aerospace Axial Flux Motor Considering the Thermal Stress of Material Lamination

Anisotropic rare-earth thick-film magnets have various applications such as MEMS (Micro Electro Mechanical Systems) devices and miniaturized electronic devices[1][2]. We have already fabricated anisotropic rare-earth film magnets by the substrate heating[3][4]. In the substrate heating process, increasing the deposition time might cause the grain size of Nd-Fe-B to increase. Our approach to anisotropic Nd-Fe-B thick-film magnets is to make them by increasing laser beam power for high deposition rate. This contribution reports the effect of laser power on several properties of anisotropic Nd-Fe-B film magnets using PLD method.
A rotated Nd-Fe-B target was ablated using an Nd-YAG pulse laser. The laser beam power was set at 2-4 W. During deposition, a Ta substrate was heated by Joule heating utilizing electric current through the substrate. J-H loops were measured with a vibrating sample magnetometer (VSM). The perpendicular loops were corrected by using the demagnetization factor of 0.8.
Figure 1 shows J-H loops of the Nd-Fe-B films deposited at each laser power. The films had the easy direction of magnetization in the plane of the perpendicular. The residual magnetic polarization ratio is defined by Jrper / Jrin , where Jrper and Jrin are the residual magnetic polarization values out-of-plane and in-plane direction, respectively. Jrper / Jrin ratio suggests that the decreasing laser power puts the easy direction of magnetization out-of-plane of the film.
Figure 2 shows X-ray diffraction patterns of samples deposited by 2 W and 4 W. The peak intensities corresponding to the c-axis prepared by laser beam power at 2 W were stronger than those for 4 W. As the relative intensity ratio of (006) / (105) increase with the decreasing laser beam power {4 W : 0.8 , 2 W : 1.3} , the increase in intensity ratio is consistent with the increase in the Jrper / Jrin value. Although it was difficult to prepare anisotropy Nd-Fe-B films with high deposition rate, we found that the crystalline texture for the Nd-Fe-B film magnets depends on the laser power. 
**References:** [1] P. Mcguiness, D. Jezeršek, S. Kobe, J. Magn. Magn. Mater., vol. 305, no. 1, pp. 177–181 (2006). 
[2] R. Fujiwara, T. Shinshi, and M. Uehara, Int. J. Automot. Technol., vol. 7, no. 2, pp. 148–155 (2013). 
[3] M. Nakano, S. Tsutsumi, T. Yanai, J. Appl. Phys., vol. 105, Issue 7, pp. 07A739-07A742 (2009). 
[4] Y. Furukawa, H. Koga, T. Yanai , IEEE Magn. Lett. , vol. 8, #5502104 (2017). 

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Effect of laser power on structural and magnetic properties of anisotropic Nd Fe

A lot of researchers have reported anisotropic (Nd or Pr) -Fe-B films prepared by a sputtering method [1]. In the experiment, the condition of annealing processes has been deeply investigated for obtaining excellent magnetic properties. We have demonstrated a miniaturized motor including PLD (Pulsed Laser Deposition)-fabricated isotropic (Nd or Pr) -Fe-B films with rare-earth rich composition compared to stoichiometric one [2]. Due to amorphous structure after the laser deposition, post-annealing is required to form the 2-14-1 phase to obtain isotropic hard magnetic films. Although a detailed investigation on the crystallization process is required to enhance isotropic magnetic properties, unfortunately there are not many reports on isotropic (Nd or Pr)-Fe-B films. In the study, we focused on the different phenomena through a post-annealing between isotropic rare-earth rich Nd-Fe-B and Pr-Fe-B films. 
Figure 1 shows coercivity of (Nd or Pr)-Fe-B films with rare earth content of 15.5 - 18.5 at. % as a function of annealing temperature in a resistance heating furnace. While the coercivity value of Nd-Fe-B films did not change up to 650 °C, the value of Pr-Fe-B films enhanced between 600 and 650 °C. Moreover, figure 2 shows the results of pulse (flash) annealing using an infrared furnace after the deposition of rare earth-rich (Nd or Pr)-Fe-B films. Although two films were annealed at the same annealing time of 1.7 s, the shoulder of a J-H loop (dotted line) for only a Pr-Fe-B film was open. X-ray diffraction patterns indicate that the 2-14-1 phase formed in the Pr-Fe-B film. In contrast, we observed that the Nd-Fe-B film had amorphous structure. Assuming that the crystallization temperatures of Pr2Fe14B and Nd2Fe14B phases are the same, the phenomenon is due to the difference in diffusion transfer of each rare earth atom during the annealing process. We consider the correlation between the diffusion transfer and the melting points (Nd: 1024 °C, Pr: 930 °C) of each element. 
**References:** [1] N. M. Dempsey et.al., Appl. Phys. Lett. Vol. A90, 092509(2007). 
[2] M. Nakano et.al., IEEE Trans. Magn. Vol. 56, 7516303(2020). 

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Fig. 1 Coercivity values of isotropic Pr-Fe-B and Nd-Fe-B films as a function of annealing temperature. (resistance heating furnace) 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/4d10335af1c50deecf36584a7dfa99b1.png) 
Fig. 2 J-H loops of Pr-Fe-B(dotted line) and Nd-Fe-B(solid line) films annealed at 1.7 s. (infrared furnace)

Investigation on crystallization process in isotropic rare earth rich (Nd or Pr)

Although Nd-Fe-B thick-films with the thickness above 10 microns have been prepared by a sputtering and a PLD (Pulsed Laser Deposition) to develop the miniaturization of devices including a magnet [1][2], it is generally said that the sputtering is not suitable for a thick-film process due to the limitation of deposition rate and the PLD has difficulty in achieving the both of large deposition area together with high deposition rate. In the case of PLD-made Nd-Fe-B films, the area has been fixed at 5 mm square. Recently, we proposed a vacuum arc deposition with a rotational substrate system to obtain an isotropic Nd-Fe-B film magnet with a 20 mm square under a deposition rate above 10 μm/h. Furthermore, compositional and thickness distribution could be reduced to ±0.4 % and ±16 %, respectively. We, however, found that the squareness of a J-H loop and (BH)max drastically deteriorated at the edge of the sample. This contribution reports improvement of the deterioration by taking advantage of Nb additive to achieve target values of magnetic properties (Hcb > 420 kA/m, Br > 0.78 T, (BH)max> 62 kJ/m3) applied to a miniaturized device. 
Figure 1 shows the relationship between coercivity (Hcb) and squareness of post-annealed Nd-Fe-B films after the vacuum arc deposition. Each symbol shows the properties of 5 mm square films cut from different area in a 20 mm square (Black circle, Black triangle: within 10 mm square from the center) and the edges (White circle, White triangle : outside of Black circle,Black triangle ). Usage of Nb additive enabled us to improve the squareness and suppress the dependence of deposition position. Moreover, Scherr’s equation using X-ray diffraction patterns reveled that the distribution of grain size due to the different deposition positions could be reduced by using Nb additive. It was also clarified that the target values except Hcb could be achieved. 
**References:** [1] N. M. Dempsey et.al., Appl. Phys. Lett. Vol. A90, 092509(2007). 
[2] M. Nakano et al., IEEE Trans. Mag. vol.56, 7516303(2020). 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/80c246b9f4b24fbd23bdeda7243fabb9.png) 
Fig. 1 Relationship between coercivity and squareness of post-annealed films deposited on different positions.

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