Two models are established to reveal the underlying coercivity mechanism for SmCo/Fe films, where one model considers a transition layer between hard and soft layers, while the other model does not consider this layer. Based on the two models, hysteresis loops, nucleation fields and coercivity are obtained by one-dimensional (1D) and three-dimensional (3D) micromagnetic methods. In particular, the calculated nucleation fields (HN) and coercivity (HC) match very well with the experimental data. It is found that the increase in the soft phase thickness (Ls) leads to a transition of the coercivity mechanism from nucleation to pinning. Such a pinning is inherently related to nucleation and has both attributes of traditional nucleation and pinning, called as a hybrid coercivity mechanism here. It is general for all hard/soft composites and can be extended to single-phased permanent magnets where defects are inevitable.
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Zhang J, Li YX, Wang F, Shen BG, Sun JR. Coercivity mechanism of nanocomposite Sm-Co/Fe multilayer films. J Appl Phys. 2010;107(4):3588.
Liu WQ, Chang C, Yue M, Yang JS, Zhang DT, Zhang JX, Liu YQ. Coercivity, microstructure, and thermal stability of sintered Nd-Fe-B magnets by grain boundary diffusion with TbH3 nanoparticles. Rare Met. 2017;36(9):718.
Wei S, Zhu MG, Fang YK, Liu ZY, Guo ZH, Li W. Microstructures and coercivity mechanism of 2:17-type Sm-Co magnets with high remanence. Rare Met. 2015. https://doi.org/10.1007/s12598-015-0513-6.
Zhao GP, Lim HS, Feng YP, Ong CK. Reversal mechanism in permanent magnetic materials. J Appl Phys. 2002;91(4):2186.
Kneller EF, Hawig R. The exchange spring magnet: a new material principle for permanent magnets. IEEE Trans Magn. 1991;27(4):3588.
Liu W, Zhang ZD, Liu JP, Chen LJ, He LL, Liu Y, Sun XK, Sellmyer DJ. Exchange coupling and remanence enhancement in nanocomposite multilayer magnets. Adv Mater. 2002;14(24):1832.
Asti G, Ghidini M, Pellicelli R, Pareti L. Magnetic phase diagram and demagnetization processes in perpendicular exchange-spring multilayers. Phys Rev B. 2006;73(9):094406.
Pellicelli R, Solzi M, Neu V, Häfner K, Pernechele C, Ghidini M. Characterization and modeling of the demagnetization processes in exchange-coupled SmCo5/Fe/SmCo5 trilayers. Phys Rev B. 2010;81(18):184430.
Li XH, Lou L, Song WP, Huang GW, Hou FC, Zhang Q, Zhang HT, Xiao JW, Wen B, Zhang XY. Novel bimorphological anisotropic bulk nanocomposite materials with high energy products. Adv Mater. 2017;29(16):1606430.
Li XH, Lou L, Song WP, Zhang Q, Huang GW, Hua YX, Zhang HT, Xiao JW, Wen B, Zhang XY. Controllably manipulating three-dimensional hybrid nanostructures for bulk nanocomposites with large energy products. Nano Lett. 2017;17(5):2985.
Dong J, Zhang Y, Zhang X, Liu Q, Wang J. Improved magnetic properties of SrFe12O19/FeCo core–shell nanofibers by hard/soft magnetic exchange-coupling effect. Mater Lett. 2014;120:9.
Zhao GP, Zhang XF, Wan XL, Xia J, Zhao Q. Angular dependence of the pinning fields for hard/soft multilayers. IEEE Trans Magn. 2015;51(11):2012004.
Li DY, Wang H, Ma ZH, Liu X, Dong Y, Liu ZQ, Zhang TL, Jiang CB. FePt/Co core/shell nanoparticle-based anisotropic nanocomposites and their exchange spring behavior. Nanoscale. 2018;10(8):4061.
Yuan XH, Zhao GP, Yue M, Ye LN, Xia J, Zhang XC. 3D and 1D calculation of hysteresis loops and energy products for anisotropic nanocomposite films with perpendicular anisotropy. J Magn Magn Mater. 2013;343:245.
Zhao GP, Wang XL. Nucleation, pinning, and coercivity in magnetic nanosystems: An analytical micromagnetic approach. Phys Rev B. 2006;74(1):012409.
Skomski R, Coey JMD. Giant energy product in nanostructured two-phase magnets. Phys Rev B. 1993;48(21):15812.
Sawatzki S, Heller R, Mickel C, Seifert M, Schultz L, Neu V. Largely enhanced energy density in epitaxial SmCo5/Fe/SmCo5 exchange spring trilayers. J Appl Phys. 2011;109(12):3922.
Neu V, Hfner K, Patra AK, Schultz L. Fully epitaxial, exchange coupled SmCo5/Fe/SmCo5 trilayers. J Phys D Appl Phys. 2006;39(11):5116.
Cui WB, Takahashi YK, Hono K. Nd2Fe14B/FeCo anisotropic nanocomposite films with a large maximum energy product. Adv Mater. 2012;24(48):6530.
Jiang JS, Pearson JE, Liu ZY, Kabius B, Trasobares S, Miller DJ, Bader SD, Lee DR, Haskel D, Srajer G, Liu JP. Improving exchange-spring nanocomposite permanent magnets. Appl Phys Lett. 2004;85(22):5293.
Si WJ, Zhao GP, Ran N, Peng Y, Morvan FJ, Wan XL. Deterioration of the coercivity due to the diffusion induced interface layer in hard/soft multilayers. Sci Rep. 2015;20(5):16212.
Donahue MJ, Porter DG. OOMMF User’s Guide, Version 1. 0. NISTIR 6376. Gaithersburg: National Institute of Standards and Technology; 1999.
Gilbert TL. A phenomenological theory of damping in ferromagnetic materials. IEEE Trans Magn. 2004;40(6):3443.
Brown WF Jr. Virtues and weaknesses of the domain concept. Rev Mod Phys. 1945;17(1):15.
Zhao GP, Zhao MG, Lim HS, Feng YP, Ong CK. From nucleation to coercivity. Appl Phys Lett. 2005;87(16):162513.
Asti G, Solzi M, Ghidini M, Neri FM. Micromagnetic analysis of exchange-coupled hard-soft planar nanocomposites. Phys Rev B. 2004;69(17):174401.
Yang W, Lei W, Yu Y, Zhu W, George TA, Li X-Z, Sellmyer DJ, Sun S. From FePt–Fe3O4 to L10-FePt–Fe nanocomposite magnets with a gradient interface. J Mater Chem C. 2015;3(27):7075.
Yu YS, George TA, Li WL, Yue LP, Fei WD, Li H, Liu M, Sellmyer DJ. Effects of total thickness on (001) texture, surface morphology, and magnetic properties of multilayer films by monatomic layer deposition. J Appl Phys. 2010;108(7):073906.
Yang W, Yu Y, Wang L, Yang C, Li H. Controlled synthesis and assembly into anisotropic arrays of magnetic cobalt-substituted magnetite nanocubes. Nanoscale. 2015;7(7):2877.
Lei W, Yu Y, Yang W, Feng M, Li H. A general strategy for synthesizing high-coercivity L10–FePt nanoparticles. Nanoscale. 2017;9(35):12855.
Yu Y, Mukherjee P, Tian Y, Li XZ, Shield JE, Sellmyer DJ. Direct chemical synthesis of L10–FePtAu nanoparticles with high coercivity. Nanoscale. 2014;6(20):12050.
Yu YS, Li H-B, Li WL, Liu M, Zhang Y, Fei WD, Sellmyer DJ. Low temperature ordering of FePt films by in situ heating deposition plus post deposition annealing. Thin Solid Films. 2010;518(8):2171.
This work was financially supported by the National Natural Science Foundation of China (Nos. 51771127, 51571126 and 51772004).
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Weng, X., Zhao, G., Tang, H. et al. Thickness-dependent coercivity mechanism and hysteresis loops in hard/soft magnets. Rare Met. 39, 22–27 (2020). https://doi.org/10.1007/s12598-019-01264-9
- Coercivity mechanism
- Hysteresis loops