Analysis of the magnetic hardening mechanism in RE-FeB permanent magnets

Abstract For the interpretation of extremely high coercive fields of RE-NdB permanent magnets in general either models of pinning or nucleation mechanisms are considered. In both cases the magnetic properties of the phase boundaries between the grains are suggested to be responsible for the actual value of H c . In this paper a detailed analysis of the temperature dependence of H c is given on the basis of the predictions of micromagnetic theories for pinning and nucleation mechanisms. It is shown that the nucleation theory leads to a far more coherent interpretation of all relevant properties of H c than the pinning theory if the effects of misaligned grains, local stray fields and reduced anisotropies in grain boundaries are taken into account.

[1]  H. Kronmüller.  Micromagnetism in hard magnetic materials , 1978 .

[2]  H. Kronmüller,et al.  Determination of intrinsic magnetic material parameters of Nd2Fe14B from magnetic measurements of sintered Nd15Fe77B8 magnets , 1986 .

[3]  G. Martinek,et al.  Angular dependence of the coercive field in sintered Fe77Nd15B8 magnets , 1987 .

[4]  D. Givord,et al.  Angular dependence of coercivity in sintered magnets , 1988 .

[5]  E. Wohlfarth,et al.  A mechanism of magnetic hysteresis in heterogeneous alloys , 1948, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[6]  M. Sagawa,et al.  The dependence of coercivity on anisotropy field in sintered R-Fe-B permanent magnets , 1986 .

[7]  William Fuller Brown,et al.  Virtues and Weaknesses of the Domain Concept , 1945 .

[8]  H. Kronmüller,et al.  Micromagnetic analysis of precipitation hardened permanent magnets , 1984 .

[9]  R. Friedberg,et al.  New Theory of Coercive Force of Ferromagnetic Materials , 1975 .

[10]  H. Kronmüller,et al.  Investigation of bloch-wall-pinning by antiphase boundaries in RCo5-compounds , 1975 .

[11]  G. Hadjipanayis,et al.  The microstructure and magnetic properties of melt-spun Fe76Nd16B8 magnetic materials , 1986 .

[12]  F. Pinkerton.  High coercivity in melt-spun Dy-Fe-B and Tb-Fe-B alloys , 1986 .

[13]  H. Kronmüller,et al.  The coercive field of sintered and melt-spun NdFeB magnets , 1987 .

[14]  M. Sagawa,et al.  Magnetizing process in R-Fe-B sintered permanent magnets studied on boron-rich R17Fe83−xBx magnets (R = Pr, Nd) , 1987 .

[15]  A. Aharoni.  Angular dependence of nucleation field in magnetic recording particles , 1986 .

[16]  G. Herzer,et al.  On the theory of nucleation fields in uniaxial ferromagnets , 1986 .

[17]  G. Hadjipanayis,et al.  Magnetic domains in rare-earth cobalt permanent magnets , 1982 .

[18]  H. Nagel.  Coercivity and microstructure of Sm(Co0.87Cu0.13)7.8 , 1979 .

[19]  H. Hilzinger.  The influence of planar defects on the coercive field of hard magnetic materials , 1977 .