Stoner-Wohlfarth Theory for Hard-Magnetic Particle Arrays

MODIFIED STONER-WOHLFARTH THEORY FOR HARD-MAGNETIC PARTICLE ARRAYS 

Traditional magnetization reversal has been discussed in the framework of the nucleation theory. The critical fields which cause an equilibrium magnetic state to change were calculated using stability analysis. In addition to the switching field these theories also revealed the reversal mode [22]. The total energy of a magnetic particle may be written in terms of the 

The total energy density of the particle is the sum of the anisotropy energy density and the Zeeman energy density in the external field  

K is the uniaxial anisotropy constant, Js = /JqMs is the spontaneous magnetic polarization, and Hex, is the external field. In equilibrium the first derivative of Eq. (1) with respect to p has to vanish. The equilibrium condition is 

The particle switches if the equilibrium condition and the instability condition 

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