Permanent Magnets based on Fe-Pt Alloys. P.D. Thang, E. Brück, K.H.J. Buschow, F.R. de Boer. Financial support by STW. Introduction Permanent magnets, motivation Experimental Sample preparation, analysis techniques Results Structure, magnetic and mechanical properties
P.D. Thang, E. Brück, K.H.J. Buschow, F.R. de Boer
Financial support by STW
Permanent magnets, motivation
Sample preparation, analysis techniques
Structure, magnetic and mechanical properties
(DYNA Dental Engineering B.V.)
- Arc-melting the pure elements (3N) in Ar
- Casting to cylinder, disc
- Homogenisation (as-quenched sample):
1325C/1h, under Ar + quenching in water fcc phase.
- Ageing (aged sample):
500-700C + quench in water fct phase.
Tensile strength: tensometer
Magnetic properties: hysteresis-loop
and … SANS
Microstructure analysis: TEM ...
Optimal hard-magnetic properties for Fe60Pt40 aged at 625C, 1h:
Br = 0.97 T, BHc = 294 kA/m, (BH)max = 118 kJ/m3
625°C, 1h: 2-5 nm
as-quenched: 1-3 nm
Fct particle size increases during the ageing.
Fct nano-size observed.
Degree of atomic order increases during the ageing.
as-quenched: 1 nm
625°C,12h: 1-3 nm
625°C,24h: 3-8 nm
625°C,48h: 8-16 nm
mn = 1.674710-24 g
n = 9.6628610-27 J/T
q = 0, 1/2 = 624 s
- Scattering from the atomic nucleus
- Magnetic scattering
- 10 Å 102 Å
- Domain and particle size
q = kf - ki
I(q,) = A(q) + B(q)sin2(/2)
B = 0 (virgin)
B = 1.8 T (in field)
B removed (remanent)
SANS dominated by randomly
oriented magnetic domains: monodisperse model
SANS dominated by particles with different magnetisation: polydisperse model
Correlation length 105 nm
(TEM: fct particles 3-8 nm)
M = 0.5 at. % Nb and 0.25 at. % Al.
Good thermal stabilisation.
Suitable for biomedical applications, e.g. denture retention.
High coercivity: correlated with the atomic order in the fcc/fct
structures and the fct grain growth.
High remanence: originated by the exchange coupling of the
soft fcc phase with the nano-sized hard fct phase.