Coercivity and squareness enhancement in ball-milled hard magnetic–antiferromagnetic composites

Sort, J.; Nogue´s, J.; Surin˜ach, S.; Mun˜oz, J. S.; Baro´, M. D.; Chappel, E.; Dupont, F.; Chouteau, G.
August 2001
Applied Physics Letters;8/20/2001, Vol. 79 Issue 8, p1142
Academic Journal
The room-temperature coercivity, H[sub C], and squareness, M[sub R]/M[sub S] (remanence/saturation magnetizations), of permanent magnet, SmCo[sub 5] powders have been enhanced by ball milling with antiferromagnetic NiO (with Ne´el temperature, T[sub N]=590 K). This enhancement is observed in the as-milled state. However, when the milling of SmCo[sub 5] is carried out with an antiferromagnet with T[sub N] below room temperature (e.g., for CoO, T[sub N]=290 K), the coercivity enhancement is only observed at low temperatures after field cooling through T[sub N]. The ferromagnetic–antiferromagnetic exchange coupling induced either by local heating during milling (SmCo[sub 5]+NiO) or field cooling (SmCo[sub 5]+CoO) is shown to be the origin of the H[sub C] increase. © 2001 American Institute of Physics.


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