Relationship between the Spontaneous Magnetization, Spontaneous Magnetostriction and Heat Capacity in the Compound Mn5Ge3

Spontaneous magnetization Ms of the ferromagnetic compound Mn5Ge3 with the Curie temperature TC=305 K has been studied in the temperature range from 2 to 400 K. The relationships between the magnetic part of the heat capacity (CMAG), the magnetic part of the volume thermal expansion coefficient (TEC) MAG, and the Ms for the compound Mn5Ge3 have been considered. It has been found that the magnetic part of the heat capacity can be well approximated by the dependence CMAG(T)=a×|dMs2/dT|–b×|dMs4/dT| with a>0 and b>0, and the magnetic part of the TEC, by the dependence  MAG=C1×dMs2/dT+C2×dMs4/dT with C1<0 and C2>0 in the whole temperature. It is assumed that the main sources in the formation of the observed CMAG(T) and MAG(T) dependences are the changes in the elastic, magnetoelastic, magnetovolume, and magnetostatic energies of the sample that appear as a result of the spontaneous magnetostrictive deformation with temperature changing.

Effects of the Electromagnetic Forces on Vibrational Behavior of the Laminated Mechanical Structure of Stator Cores

Stator laminations can have mutual excitation sources depending to the inertial forces that can excite the mechanical resonances and radial components of the electromagnetic forces that vary with the magnetic flux changes and the magnetostrictive forces. Magnetostrictive forces can appear depending to the material properties of the plates and have mechanical and magnetic causes Mechanical properties of the lamination plates can be determined both in numerical and experimental methods. Magnetostrictive effects of the laminations have significant contribution to the audible noise of electric motors. The combined effects of radial components of electromagnetic forces and magnetostrictive deformation can cause further amplification problems of noise. This study investigates the effects of magnetostrictive forces on the laminated mechanical structure of stator core by referring to the changes of the plate materials depending to applicable heat treatments, magnetic properties and silicon alloying that were all considered as factors to modify the effects of magnetostriction.