L. Folks et R. Street, ANALYSIS AND INTERPRETATION OF TIME-DEPENDENT MAGNETIC PHENOMENA (INVITED), Journal of applied physics, 76(10), 1994, pp. 6391-6395
Time dependence of intensity of magnetization is the result of thermal
activation of metastable domain processes. The simple (M,H) represent
ation of magnetic behavior may be extended to include time dependent e
ffects using a constitutive equation. Magnetic processes may be descri
bed by the movement of a point over a three-dimensional surface with c
oordinates M, H, and M. The parameters required to define the surface,
Lambda (or fluctuation field H-f) and chi, may be derived from measur
ements of the time dependence of magnetization. A review of the utiliz
ation of the constitutive equation is given and simple methods for obt
aining the material parameters from conventional magnetic viscosity me
asurements (under constant applied field conditions) are described. Me
asurements of Lambda in particular provide additional quantitative inf
ormation on magnetization processes which may be compared with predict
ions of proposed models of magnetization. The results of measurements
of Lambda and susceptibility chi for CrO2 powders and sintered and mel
t-quenched rare earth-transition metal borides are presented. Conclusi
ons about the magnetization mechanisms of these materials are discusse
d.