TY - JOUR

T1 - A single integral expression for the magnetisation
of a textured superparamagnetic system

AU - Cregg, P J

AU - Bessais, Lotfi

PY - 1999

Y1 - 1999

N2 - A superparamagnetic system consists of many single domain particles with relaxation times smaller than the time of
measurement (t=100 s), with the result that thermal agitation leads to zero magnetisation in zero field,M(H=0)=0 for t>100 s. For particles in a fluid, an external field will result in a magnetisation given by the Langevin function as inparamagnetism. However, particles fixed into position in the presence of a field, obtain an orientational texture. We still find M(H=0)=0, but the magnetisation is not given by the Langevin function. The model of Chantrell et al. can yield an expression for M capable of including texture. This requires the calculation of the partition function of the system
which is a double integral in the coordinate system used. Here we reduce this double integral to a single integral.

AB - A superparamagnetic system consists of many single domain particles with relaxation times smaller than the time of
measurement (t=100 s), with the result that thermal agitation leads to zero magnetisation in zero field,M(H=0)=0 for t>100 s. For particles in a fluid, an external field will result in a magnetisation given by the Langevin function as inparamagnetism. However, particles fixed into position in the presence of a field, obtain an orientational texture. We still find M(H=0)=0, but the magnetisation is not given by the Langevin function. The model of Chantrell et al. can yield an expression for M capable of including texture. This requires the calculation of the partition function of the system
which is a double integral in the coordinate system used. Here we reduce this double integral to a single integral.

U2 - doi:10.1016/S0304-8853(99)00269-3

DO - doi:10.1016/S0304-8853(99)00269-3

M3 - Article

VL - 203

SP - 265

EP - 267

JO - Journal of Magnetism and Magnetic Materials

JF - Journal of Magnetism and Magnetic Materials

SN - 0304-8853

ER -