The reversibility of magnetic properties of sintered SmCo₅permanent magnets

Magnetic and anomalous magnetic viscosity in the bulk amorphous ferromagnet and partially amorphous ferromagnet

“…In bulk amorphous ferromagnets thermal remagnetisation is about four times larger than spontaneous remagnetisation. Thermal remagnetisation is a well known effect in crystalline permanent magnet materials, being first reported in sintered SmCo 5 magnets [28]. The effect is largest in nucleation controlled magnets, such as SmCo 5 and NdFeB where it may attain values of 80% and 12% of the saturation magnetic polarisation, respectively, and smallest, or almost non-existent, in pinning controlled magnets such as Sm 2 Co 17 , where it may attain a value of 3% of magnetic saturation [29][30][31].…”

Thermal and spontaneous remagnetization in ferromagneticNd3(Fe,Ti)29andCollocott1, Dunlop2, Watterson3 2007Phys. Rev. B

“…Thermal remagnetization has been studied in SmCo 5 permanent magnets [2][3][4][5][6] ͑primarily in relation to the stabilization of magnetic properties͒, in Sm 2 Co 17 permanent magnets, 6,7 in Nd-Fe-B sintered magnets, 5,8 and in the two-phase spring magnet Nd 4 Fe 77 B 19 . 9 The effect is largest in the nucleation controlled permanent magnets SmCo 5 and Nd-Fe-B.…”

Theory of thermal remagnetization of permanent magnets

“…The contribution of the hard grains is more difficult to calculate, due to the memory effect. Let us consider the probability w ↓↑ (H s ) that a hard grain with a given H s was switched by H (1) ext and switched back by H (2) ext afterwards.…”

“…To calculate this probability it is inevitable to make an assumption on the correlation between the fluctuation of the local field H 1 which acts on a grain if H (1) ext is applied and the fluctuation of H 2 according to the external field H (2) ext . Of course, if H (2) ext is only slightly different from H (1) ext it is unlikely that the neighbourhood of a grain changes considerably, so that H 1 and H 2 should be strongly correlated. With increasing distance between H (1) ext and H (2) ext this correlation will vanish, due to the multitude of switching processes.…”

“…The largest TR-effect, i.e. more than 80 % of the saturation magnetization at the initial temperature, has been observed in well-aligned sintered SmCo 5 for a closed magnetic circuit [2,3]. In open circuits the TR depends strongly on the demagnetization factor N of the sample [4,5].…”