Microstructure, magnetic properties and magnetic hardening in 2 : 17 Sm–Co magnets
-
W. Tang
,
Y. Zhang
Abstract
A comprehensive and systematic study has been made on Sm(Co, Fe, M, L)z magnets (M = Cu or Ni, and L = Zr or Ti) to completely understand the effects of composition and processing on the microstructure and magnetic properties of magnets. Ti-containing magnets do not have a lamellar phase but exhibit only a cellular microstructure, resulting in a much lower coercivity (below 10 kOe). Ni-containing magnets exhibit a perfect cellular/lamellar microstructure, but without a large domain wall energy gradient at the interface of the 2 : 17 and 1 : 5 phases, leading to a low coercivity. Only in the magnets containing both Cu and Zr, a uniform and stable cellular/lamellar microstructure with a high domain wall energy gradient across the 1 : 5 phase is formed, resulting in high coercivity. These results indicate that the conditions for effective magnetic hardening are: (1) Formation of a cellular/lamellar microstructure, and (2) establishment of a domain wall energy gradient at the cell boundaries. Based on all of these experimental results, the magnetization reversal mechanism of 2 : 17 Sm–Co magnets can be explained by both the domain wall pinning and nucleation models. The nucleation mechanism holds at any temperature in the Cu-rich magnets, and only above the Curie temperature of the 1 : 5 phase in the alloys with the lower Cu content. In these cases, the 2 : 17 cells become magnetically decoupled.
Abstract
Sm(Co, Fe, M, L)z-Magnete (M = Cu oder Ni, L = Zr oder Ti) wurden detailliert und systematisch untersucht, um die Auswirkungen von Zusammensetzung und Herstellungsprozess solcher Magnete auf deren Gefüge und ihre magnetische Eigenschaften zu untersuchen. Magnete, die Ti enthalten, weisen keine lamellare Phase auf, sondern nur eine zellulare Mikrostruktur, und haben daher eine sehr kleine Koerzitivkraft (weniger als 10 kOe). Magnete mit Ni besitzen eine perfekte zelluläre Mikrostruktur, aber an den 2 : 17- und 1 : 5-Phasengrenzschichten ist der Gradient der Domänenwandenergie nicht sehr hoch, was ebenfalls zu einer niedrigen Koerzitivkraft führt. Eine gleichmäßige und stabile zelluläre/lamellare Mikrostruktur mit einem hohen Gradienten der Domänenwandenergie an der 1 : 5-Phasengrenzschicht hingegen führt zu einer großen Koerzitivkraft. Dies ist nur in Magneten, die sowohl Cu als auch Zr enthalten, der Fall. Die Ergebnisse lassen auf die folgenden Bedingungen für eine effektive magnetische Härtung schließen: (1) Bildung einer zellulären/lamellaren Mikrostruktur und (2) Ausbildung eines hohen Domänenwandenergie-Gradienten an der Zellwand. Durch die Resultate kann der Mechanismus der Ummagnetisierung eines 2 : 17-Sm–Co-Magneten durch Verankerung der Domänenwände und durch Keimbildung erklärt werden. In Cu-reichen Magneten tritt der Keimbildungsmechanismus im gesamten Temperaturbereich auf, in Magneten mit kleinerem Cu-Gehalt nur oberhalb der Curie-Temperatur der 1 : 5-Phase. In diesen Fällen sind die 2 : 17-Zellen magnetisch voneinander isoliert.
Dedicated to Professor Dr. Helmut Kronmüller on the occasion of his 70th birthday
The authors gratefully acknowledge the support of the MURI 96 programme and DARPA 2000 Met-Materials programme.
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© 2002 Carl Hanser Verlag, München
Articles in the same Issue
- Frontmatter
- Editorial
- Editorial
- Articles/Aufsätze
- Interplay between chemical and magnetic roughness of Pt in a Pt/Co bilayer investigated with X-ray resonant magnetic reflectometry
- Thermal stability and magnetic anisotropy dispersion in high-density hard-disk media
- Thickness dependence of magnetization structures in thin Permalloy rectangles
- Solving the selectivity problem in magnetic random access memories using configurations that form C-states
- Second-order magnetoelastic effects: From the Dirac equation to the magnetic properties of ultrathin epitaxial films for magnetic thin-film applications
- Magnetic relaxation in nanocrystalline systems: linking Monte Carlo steps with time
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- The character and role of grain boundaries in NdFeB-type alloys and magnets
- Magnetic domain structure and spin reorientation process
- Magnetic properties of Tb(Fe, Mo)12 and Tb(Fe, Mo)12C compounds
- Microstructure, magnetic properties and magnetic hardening in 2 : 17 Sm–Co magnets
- Micromagnetism and microstructure – tailoring of high-performance permanent magnets
- Metastable alloys at moderate cooling rates
- Thermal critical phenomena and crossover between critical regimes in ferromagnets with long-range interactions
- Vacancies in thermal equilibrium and ferromagnetism near the Curie temperature
- The vortex lattice in superconductors
- Functional substrates – a novel approach to tailor transport properties and flux-line pinning in YBa2Cu3O7 – x thin films
- Superconducting permanent magnets and their application in magnetic levitation
- Magneto-optical studies of flux pinning in high-temperature superconductors
- Atomic transport in amorphous metals
- A novel technique for measuring diffusivities of short-lived radioisotopes in solids
- Hydrogen four-level tunnel systems in substitutional body-centred cubic alloys
- Magnetic relaxation phenomena in cobalt
- The Verwey transition in magnetite as studied by means of definite impurity doping
- Notifications/Mitteilungen
- Personal/Personelles
- Bücher/Books
- Conferences/Konferenzen
- DGM Training/DGM Fortbildung
Articles in the same Issue
- Frontmatter
- Editorial
- Editorial
- Articles/Aufsätze
- Interplay between chemical and magnetic roughness of Pt in a Pt/Co bilayer investigated with X-ray resonant magnetic reflectometry
- Thermal stability and magnetic anisotropy dispersion in high-density hard-disk media
- Thickness dependence of magnetization structures in thin Permalloy rectangles
- Solving the selectivity problem in magnetic random access memories using configurations that form C-states
- Second-order magnetoelastic effects: From the Dirac equation to the magnetic properties of ultrathin epitaxial films for magnetic thin-film applications
- Magnetic relaxation in nanocrystalline systems: linking Monte Carlo steps with time
- Effect of domain size on the magneto-elastic damping in amorphous ferromagnetic metals
- The character and role of grain boundaries in NdFeB-type alloys and magnets
- Magnetic domain structure and spin reorientation process
- Magnetic properties of Tb(Fe, Mo)12 and Tb(Fe, Mo)12C compounds
- Microstructure, magnetic properties and magnetic hardening in 2 : 17 Sm–Co magnets
- Micromagnetism and microstructure – tailoring of high-performance permanent magnets
- Metastable alloys at moderate cooling rates
- Thermal critical phenomena and crossover between critical regimes in ferromagnets with long-range interactions
- Vacancies in thermal equilibrium and ferromagnetism near the Curie temperature
- The vortex lattice in superconductors
- Functional substrates – a novel approach to tailor transport properties and flux-line pinning in YBa2Cu3O7 – x thin films
- Superconducting permanent magnets and their application in magnetic levitation
- Magneto-optical studies of flux pinning in high-temperature superconductors
- Atomic transport in amorphous metals
- A novel technique for measuring diffusivities of short-lived radioisotopes in solids
- Hydrogen four-level tunnel systems in substitutional body-centred cubic alloys
- Magnetic relaxation phenomena in cobalt
- The Verwey transition in magnetite as studied by means of definite impurity doping
- Notifications/Mitteilungen
- Personal/Personelles
- Bücher/Books
- Conferences/Konferenzen
- DGM Training/DGM Fortbildung
