Magnetic anisotropy constants

The temperature dependence of the magnetic hyperfine splitting in spectra of interacting nanoparticles may be described by a mean field model [75-77]. In this model it is assumed that the magnetic energy of a particle, p, with volume V and magnetic anisotropy constant K, and which interacts with its neighbor particles, q, can be written... 

The magnetic properties of iron oxides can be determined using Mossbauer spectroscopy, neutron powder diffraction and magnetometry (see Chap. 7). The characteristic parameters are the magnetic moment, the permeability, the saturation magnetization, the magnetic anisotropy constants and the Bhf (Tab. 6.2). 

Figure 26. Effect of annealing temperature on magnetic anisotropy constant and activation volume of FePt C cluster films with 45 vol. % C.

Magnetic anisotropy constants Kj, K2, and K3 can be found from magnetization curves measured along various crystallographic directions. This method is based on fitting of an experimental magnetization curve Iexp(H) by a calculated dependence Icaic(H), where Ki, K2, K3 are fit parameters. The values providing the best fit are considered as experimentally obtained constants. 

A B20 crystal field parameter decreases as hydrogen atoms concentration increases (Fig. 6) and, therefore, the rare-earth sublattice magnetic anisotropy constant Kir (K1r -J2B20Bj2(x), where Bj2(x) is the 2nd order generalized Brillouin function) also decreases. Hydrogenation leads to a decrease of the... 

Before MFM measurements all films were characterized using magnetooptical Kerr effect millimagnetometry. That provides remanence, coercivity, and magnetic anisotropy constants. 

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