The resonance decay function method in the determination of the pre-factor of the Neel relaxation time of single-domain nanoparticles

作者：Fannin P C^*; Marin C N; Couper C

来源：Journal of Magnetism and Magnetic Materials, 2011, 323(10): 1242-1245.

DOI：10.1016/j.jmmm.2010.11.014

• Magnetic fluid
• Dynamic susceptibility
• Ferromagnetic resonance

In its simple form, the relaxation time of the Neel relaxation process of the magnetic moment of single-domain particles is given by tau(N)=tau(0N)exp(sigma), sigma being the ratio of anisotropy energy to thermal energy. The pre-factor, tau(0N), is normally given a value of 10(-9) s, but values ranging from 10(-8) to 10(-12) s have been reported in literature. Here, by means of the field and frequency dependence of the complex magnetic susceptibility, chi(omega,H)=chi'(omega,H)-i chi ''(omega,H), of a magnetic fluid sample, in the MHz-GHz range, in conjunction with the determination of the sample decay function, b(t), the pre-factor tau(0N) is determined. b(t) is readily obtained through the inverse Fourier transformation relationship, which exists between b(t) and chi ''(omega).

• 出版日期2011-5