Magnetic susceptibility and magnetization fluctuation measurements of mixed Gadolinium-Yttrium Iron Garnets

TL;DR

This study investigates the magnetic properties and fluctuations of Gadolinium-Yttrium Iron Garnet ceramics across various temperatures and frequencies, linking magnetization noise to permeability measurements and discussing implications for precision applications.

Contribution

It provides comprehensive measurements of permeability and magnetization fluctuations in Gd-YIG ceramics, demonstrating the connection via fluctuation-dissipation theorem and exploring potential applications.

Findings

Magnetic viscosity affects permeability at low frequencies.

Magnetization fluctuations are consistent with permeability data.

Implications for precision magnetic measurements are discussed.

Abstract

We study the magnetic properties of Gadolinium-Yttrium Iron Garnet ($\text{Gd}_{x}\text{Y}_{3-x}\text{Fe}_5\text{0}_{12}$, $x=3,1.8$) ferrite ceramics. The complex initial permeability is measured in the temperature range 2 K to 295 K at frequency of 1 kHz, and in the frequency range 100 Hz to 200 MHz at temperatures 4 K, 77 K, and 295 K. The magnetic viscosity-induced imaginary part of the permeability is observed at low frequencies. Measurements of the magnetization noise are made at 4 K. Using the fluctuation-dissipation theorem, we find that the observed magnetization fluctuations are consistent with our measurements of the low-frequency imaginary part of permeability. We discuss some implications for proposed precision measurements as well as other possible applications.