Higher harmonics of theacsusceptibility: Analysis of hysteresis effects in ultrathin ferromagnets

Abstract

The initial ac susceptibility is used to monitor the higher harmonic susceptibilities n (T, 0 ) as a function of temperature. To our knowledge, for the first time we present n (T, 0 ) up to nϭ11 for a (Fe 2 /V 5 ) 50 superlattice in the ultrathin-film limit. A detailed analysis of n (T, 0 ) yields the full temperature-dependent hysteresis loops, including the coercive field H C (T) and the saturation magnetization M S (T), with high accuracy close to the Curie temperature T C . We show that this type of analysis allows for an independent determination of T C . In addition, the n (T, 0 ) are calculated in the framework of a mean-field theory which compares well with the experimental data.

Probing Magnetic Phases in Different Systems using Linear and Non Linear Susceptibility

“…However, there are a few experimental studies of the third ordered susceptibility (χ 3 ) on ferromagnetic systems [30,33,34] which though predominantly qualitative in nature have included attempts on characterizing these transitions by the determination of the critical exponents. Recently, a study has been made to understand the hysteresis effect in ferromagnet through the measurement of non-linear susceptibilities [35].…”

Study of magnetization processes using higher harmonic ac‐susceptibility

“…This again shows that the study of higher harmonic susceptibilities yields detailed information on the magnetization hysteresis loop. Our work differs from the earlier work of Rüdt et al [36] in two aspects: (i) structural inhomogeneity of the sample is included and modelled by using distribution functions for the coercive and unidirectional anisotropy fields and (ii) the dc-field dependence is measured and used as an alternative method to determine the coercive field. The use of the Preisach model obviously leads to a better quantitative agreement between measured and calculated ac-susceptibility curves than obtained for a single hysteron.…”

“…Whereas most of the work on magnetic systems has focused on the study of the phase transition in ferromagnets [31,32,34,36] and spin glasses [24,25,33,35] as well as on the blocking of superparamagnetic particles [33,35], in the work of Rüdt et al [36] a model based on the Heisenberg Hamiltonian was developed for the analysis of the ferromagnetic hysteresis loop of Fe/V-multilayers using higher harmonic susceptibilities. In the present work a similar approach is followed using the Preisach model.…”

“…Since ac-susceptibility is a fast technique and since measurements of higher harmonic susceptibilities can be performed up to high values of the harmonic number using standard lock-in measurements, this technique offers an alternative to magnetometer measurements [36].…”

“…Measurements of higher harmonic susceptibilities have been used to characterize the magnetic response of superconductors [28][29][30] and magnetic systems [24,25,[31][32][33][34][35][36]. Whereas most of the work on magnetic systems has focused on the study of the phase transition in ferromagnets [31,32,34,36] and spin glasses [24,25,33,35] as well as on the blocking of superparamagnetic particles [33,35], in the work of Rüdt et al [36] a model based on the Heisenberg Hamiltonian was developed for the analysis of the ferromagnetic hysteresis loop of Fe/V-multilayers using higher harmonic susceptibilities.…”