Slow cooling conditions for texturing ferromagnetic materials by solidification in a magnetic field

Solidification of giant magnetostrictive materials TbFe1.9, DyFe1.9, and Tb0.3Dy0.7Fe1.9 in a magnetic field has been investigated. Suppressing the turbulence in the melt is a key factor in texturing the magnetic materials. Those factors which influence convective flow during the course of solidification are discussed, and a critical Rayleigh number Rac can be used to reflect the state of turbulence at various cooling rates. Once the value of Rac in a magnetic field is larger than that of the practical Rayleigh number Ra in the melt, the temperature oscillations will be restrained, and the texture along the easy magnetic axis for those ferromagnetic materials will be dominant in the sample.