Field-dependent AC susceptibility of itinerant ferromagnets

Abstract

Whereas dc measurements of magnetic susceptibility, $\chi$, fail to distinguish between local and weak itinerant ferromagnets, radio-frequency (rf) measurements of $\chi$ in the ferromagnetic state show dramatic differences between the two. We present sensitive tunnel-diode resonator measurements of $\chi$ in the weak itinerant ferromagnet ZrZn${}_2$ at a frequency of 23 MHz. Below Curie temperature, $T_C\approx 26$ K, the susceptibility is seen to increase and pass through a broad maximum at approximately 15 K in zero applied dc magnetic field. Application of a magnetic field reduces the amplitude of the maximum and shifts it to lower temperatures. The existence and evolution this maximum with applied field is not predicted by either the Stoner or self-consistent renormalized (SCR) spin fluctuations theories. For temperatures below $T_C$ both theories derive a zero-field limit expression for $\chi$. We propose a semi-phenomenological model that considers the effect of the internal field from the polarized fraction of the conduction band on the remaining, unpolarized conduction band electrons. The developed model accurate describes the experimental data.

References in corpus (8)

• Meissner - London state in superconductors of rectangular cross-section in perpendicular magnetic field
• Magnetic Order and Dynamics in an Orbitally Degenerate Ferromagnetic Insulator
• Radio-frequency impedance measurements using a tunnel-diode oscillator (TDO) technique
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• Superconductivity induced by spark erosion in ZrZn2
• Precise measurements of radio-frequency magnetic susceptibility in (anti)ferromagnetic materials
• Contact-less measurements of Shubnikov-de Haas oscillations in the magnetically ordered state of CeAgSb${}_2$ and SmAgSb${}_2$ single crystals
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