Yu Ning, Ji Jingwen (College of Sciences , Northeastern University, Shenyang 110004, China)
<正> The expression of critical size of ferromagnetic microcrystal in an external magnetic field with an intensity of H is derived by means of comparing energies of domain structure states. The ferromagnetic microcrystal here means an ferromagnetic single crystal with the size which is smaller than L0, and L0 is the critical value of the size of single-domain particles at the external magnetic field intensity H = 0. Also, the coercive strength H(Ls) relating to the size of microcrystal Ls is given and quantitatively evaluated with the material SmCo5 as an instance. It is thus concluded that if L0 > Ls > LC, the antimagnetization of microcrystal will be subjected to a multi-domain process just like the particles of a size greater than L0, only if Ls < LC, the anti-magnetizaton will be carried on in accordance with the Stoner-Wohlforth mechanism(LC is the maximum size of microcrystal with MHcth). It is suggested that the material RECo5 is available to make an advanced magnet with MHC=2 K/Ms.
magnetization mechanism; coercive force; ferromagnetic microcrystal
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