Domain-wall pinning at inhomogeneities of arbitrary cross-sectional geometry

The coercivity of cellular Sm-Co based permanent magnets is investigated by model calculations. The grain boundaries responsible for the pinning coercivity are modeled as planar inhomogeneities with arbitrary cross-sectional geometry. The calculation yields a physically transparent integral equation for the pinning energy, whose derivative is the pinning force. The theory rationalizes experimental data on a semiquantitative level, but without adjustable parameters, and bridges the gap between smooth concentration gradients and abrupt interfaces. Explicit results are obtained for sinusoidal profiles, for very thin grain boundaries, and for profiles intermediate between attractive and repulsive pinning. The corrections predicted by the present model elucidate the occurrence of coercivity when the main and grain-boundary phases have the same wall energy.

[1]  T. Gemming,et al.  Microchemistry and magnetization reversal mechanism in melt-spun 2:17-type Sm-Co magnets , 2003 .

[2]  R. Skomski.  TOPICAL REVIEW: Nanomagnetics , 2003 .

[3]  R. Skomski.  Nanomagnetics , 2003 .

[4]  D. Sellmyer,et al.  Coercivity of titanium-substituted high-temperature permanent magnets , 2001 .

[5]  G. Hadjipanayis,et al.  High temperature 2:17 magnets: relationship of magnetic properties to microstructure and processing , 2000 .

[6]  Ralph Skomski,et al.  Sm–Co–Cu–Ti high-temperature permanent magnets , 2000 .

[7]  Junliang Yang,et al.  Abnormal temperature dependence of intrinsic coercivity in sintered Sm–Co-based permanent magnets , 2000 .

[8]  B. Streibl,et al.  Domain wall pinning in high temperature SM(Co, Fe, Cu, Zr)7-8 magnets , 2000 .

[9]  D. Goll,et al.  Melt-spun precipitation-hardened Sm2(Co,Cu,Fe,Zr)17 magnets with abnormal temperature dependence of coercivity , 2000 .

[10]  Michael H. Walmer,et al.  Sm2(Co,Fe,Cu,Zr)17 magnets for use at temperature ⩾400 °C , 1998 .

[11]  M. McHenry,et al.  Structure and magnetic properties of SmCo7−xZrx alloys (x=0–0.8) , 1998 .

[12]  M. McHenry,et al.  Structure and Magnetic Properties of SmCo7-xZrx Alloys (x=0 to 0.8) , 1998, 7th Joint MMM-Intermag Conference. Abstracts (Cat. No.98CH36275).

[13]  Ralph Skomski,et al.  Domain-wall curvature and coercivity in pinning type Sm–Co magnets , 1997 .

[14]  J. Coey.  Rare-earth iron permanent magnets , 1996 .

[15]  J. Coey,et al.  Giant energy product in nanostructured two-phase magnets. , 1993, Physical review. B, Condensed matter.

[16]  Kaplesh Kumar,et al.  RETM5 and RE2TM17 permanent magnets development , 1988 .

[17]  J. Fidler,et al.  Coercivity of precipitation hardened cobalt rare earth 17:2 permanent magnets , 1982 .

[18]  P. Skalicky,et al.  Microstructure of precipitation hardened cobalt rare earth permanent magnets , 1982 .

[19]  J. Livingston,et al.  Microstructure of aged (Co,Cu,Fe)7Sm magnets , 1977 .

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

[21]  J. W. Brown.  Thermal Fluctuations of a Single-Domain Particle , 1963 .