Magnetic Resonance of Ferrites with a Compensation Temperature

Abstract

Calculations of the resonance fields as a function of temperature and of resonance frequency as a function of field for temperatures near the compensation temperature for lithium-chromium ferrite and gadolinium garnet are given. For the latter case, a comparison is made between the assumption of zero anisotropy and an assumed negative anisotropy.

Quantitative analysis of spin wave dynamics in ferrimagnets across compensation points

“…We model the ferrimagnetic system with two coupled Landau-Lifshitz-Gilbert (LLG) equations and two magnetization vector fields, corresponding to the RE and TM moments, following an approach used to analyze the ferromagnetic ressonance (FMR) of compensated ferrimagnetic garnets and ferrites [6,7] interaction (J), and dipolar interactions:…”

“…Two remarkable temperatures appear: the magnetic and the angular compensation temperatures (T MC and T AC ) where, respectively, M S or L S vanishes [2][3][4][5]. Previous studies have reported a large and complex variation of the spin wave (SW) frequencies with the balance between sublattices [6][7][8][9][10]. Different approaches have been used to model the ferrimagnetic dynamics of RE-TMs, its internal energy and dynamics: the effective ferromagnet model [11,12] (see also Appendix A), AF-inspired models that describe the system in terms of the Néel and magnetization vectors (l, m) [13], and models based on two distinct but coupled sublattices of RE and TM moments [7].…”

“…Previous studies have reported a large and complex variation of the spin wave (SW) frequencies with the balance between sublattices [6][7][8][9][10]. Different approaches have been used to model the ferrimagnetic dynamics of RE-TMs, its internal energy and dynamics: the effective ferromagnet model [11,12] (see also Appendix A), AF-inspired models that describe the system in terms of the Néel and magnetization vectors (l, m) [13], and models based on two distinct but coupled sublattices of RE and TM moments [7]. The SW spectrum, and its variation with field and temperature, provides a thorough test for these different models: it is sensitive to the different interactions (e.g., anisotropy and interlattice exchange coupling) and to the details of the dynamics that determine the properties of the different SW modes.…”